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Alternate history (also alternative history, althist, AH) is a genre of speculative fiction of stories in which one or more historical events occur and are resolved differently than in real life.     As conjecture based upon historical fact, alternate history stories propose What if? scenarios about crucial events in human history, and present outcomes very different from the historical record. Alternate history also is a subgenre of literary fiction, science fiction, and historical fiction; as literature, alternate history uses the tropes of the genre to answer the What if? speculations of the story.
The terms, Allohistory (other history), counterfactualism, and virtual history are another terms for the genre of alternative history. Moreover, the term alternate history is used for the genre in the US.  While in the Spanish, French, German, and Portuguese, Italian, Catalan, and Galician languages, the terms Uchronie, ucronia, ucronía, and Uchronie identify the alternate history genre, from which derives the English term Uchronia, composed of the Greek prefix ου- ("not", "not any", and "no") and the Greek word χρόνος (chronos) "time", to describe a story that occurs "[in] no time"; analogous to a story that occurs in utopia, "[in] no place". The term Uchronia also is the name of the list of alternate-history books, uchronia.net. 
Often described as a subgenre of science fiction, Alternative History is a genre of fiction wherein the author speculates upon how the course of history might have been altered if a particular historical event had an outcome different from the real life outcome.  An alternate history requires three conditions: (i) A point of divergence from the historical record, before the time in which the author is writing; (ii) A change that would alter known history; and (iii) An examination of the ramifications of that alteration to history.  Occasionally, some types of genre fiction are misidentified as alternative history, specifically science fiction stories set in a time that was the future for the writer, but now is the past for the reader, such as the novels 2001: A Space Odyssey (1968), by Arthur C. Clarke and Nineteen Eighty-Four (1949), by George Orwell, because the authors did not alter the history of the past when they wrote the stories.  Some alternative history stories feature the tropes of time travel between histories, and the psychic awareness of the existence of an alternative universe, by the inhabitants of a given universe; and time travel that divides history into various timestreams.[ citation needed]
Similar to the genre of Alternative History, there is also the genre of the Secret History of an event, which can be either fictional or non-fictional, documents events that might have occurred in history, but which had no effect upon the recorded historical outcome.   Alternative history also is thematically related to, but distinct from, Counterfactual History, which is a form of historiography that attempts to answer the What if? speculations that arise from counterfactual conditions in order to understand what did happen.  As a method of historical research, counterfactual history explores historical events with an extrapolated timeline in which key historical events either did not occur or had an outcome different from the historical record. 
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The earliest example of alternate (or counterfactual) history is found in Livy's Ab Urbe Condita Libri (book IX, sections 17–19). Livy contemplated an alternative 4th century BC in which Alexander the Great had survived to attack Europe as he had planned; asking, "What would have been the results for Rome if she had been engaged in a war with Alexander?"    Livy concluded that the Romans would likely have defeated Alexander.    An even earlier possibility is Herodotus's Histories, which contains speculative material. 
Another example of counterfactual history was posited by cardinal and Doctor of the Church Peter Damian in the 11th century. In his famous work De Divina Omnipotentia, a long letter in which he discusses God's omnipotence, he treats questions related to the limits of divine power, including the question of whether God can change the past,  for example, bringing about that Rome was never founded:   
I see I must respond finally to what many people, on the basis of your holiness’s [own] judgment, raise as an objection on the topic of this dispute. For they say: If, as you assert, God is omnipotent in all things, can he manage this, that things that have been made were not made? He can certainly destroy all things that have been made, so that they do not exist now. But it cannot be seen how he can bring it about that things that have been made were not made. To be sure, it can come about that from now on and hereafter Rome does not exist; for it can be destroyed. But no opinion can grasp how it can come about that it was not founded long ago... 
One early work of fiction detailing an alternate history is Joanot Martorell's 1490 epic romance Tirant lo Blanch, which was written when the loss of Constantinople to the Turks was still a recent and traumatic memory for Christian Europe. It tells the story of the knight Tirant the White from Brittany who travels to the embattled remnants of the Byzantine Empire. He becomes a Megaduke and commander of its armies and manages to fight off the invading Ottoman armies of Mehmet II. He saves the city from Islamic conquest, and even chases the Turks deeper into lands they had previously conquered.
One of the earliest works of alternate history published in large quantities for the reception of a large audience may be Louis Geoffroy's Histoire de la Monarchie universelle : Napoléon et la conquête du monde (1812–1832) (History of the Universal Monarchy: Napoleon and the Conquest of the World) (1836), which imagines Napoleon's First French Empire emerging victorious in the French invasion of Russia in 1812 and in an invasion of England in 1814, later unifying the world under Bonaparte's rule. 
In the English language, the first known complete alternate history is Nathaniel Hawthorne's short story " P.'s Correspondence", published in 1845. It recounts the tale of a man who is considered "a madman" due to his perceptions of a different 1845, a reality in which long-dead famous people, such as the poets Robert Burns, Lord Byron, Percy Bysshe Shelley and John Keats, the actor Edmund Kean, the British politician George Canning, and Napoleon Bonaparte, are still alive.
The first novel-length alternate history in English would seem to be Castello Holford's Aristopia (1895). While not as nationalistic as Louis Geoffroy's Napoléon et la conquête du monde, 1812–1823, Aristopia is another attempt to portray a Utopian society. In Aristopia, the earliest settlers in Virginia discover a reef made of solid gold and are able to build a Utopian society in North America.
In 1905, H. G. Wells published A Modern Utopia. As explicitly noted in the book itself, Wells's main aim in writing it was to set out his social and political ideas, the plot serving mainly as a vehicle to expound them. This book introduced the idea of a person being transported from a point in our familiar world to the precise geographical equivalent point in an alternate world in which history had gone differently. The protagonists undergo various adventures in the alternate world, and then are finally transported back to our world, again to the precise geographical equivalent point. Since then, that has become a staple of the alternate history genre.
A number of alternate history stories and novels appeared in the late 19th and early 20th centuries (see, for example, Joseph Edgar Chamberlin's The Ifs of History  and Charles Petrie's If: A Jacobite Fantasy ).  In 1931, British historian Sir John Squire collected a series of essays from some of the leading historians of the period for his anthology If It Had Happened Otherwise. In that work, scholars from major universities, as well as important non-academic authors, turned their attention to such questions as "If the Moors in Spain Had Won" and "If Louis XVI Had Had an Atom of Firmness". The essays range from serious scholarly efforts to Hendrik Willem van Loon's fanciful and satiric portrayal of an independent 20th-century New Amsterdam, a Dutch city-state on the island of Manhattan. Among the authors included were Hilaire Belloc, André Maurois, and Winston Churchill.
One of the entries in Squire's volume was Churchill's "If Lee Had Not Won the Battle of Gettysburg", written from the viewpoint of a historian in a world in which the Confederacy had won the American Civil War. The entry considers what would have happened if the North had been victorious (in other words, a character from an alternate world imagines a world more like the real one we live in, although it is not identical in every detail). Speculative work that narrates from the point of view of an alternate history is variously known as " recursive alternate history", a "double-blind what-if", or an "alternate-alternate history".  Churchill's essay was one of the influences behind Ward Moore's alternate history novel Bring the Jubilee[ citation needed] in which General Robert E. Lee won the Battle of Gettysburg and paved the way for the eventual victory of the Confederacy in the American Civil War (named the "War of Southron Independence" in this timeline). The protagonist, the autodidact Hodgins Backmaker, travels back to the aforementioned battle and inadvertently changes history, which results in the emergence of our own timeline and the consequent victory of the Union instead.
The American humorist author James Thurber parodied alternate history stories about the American Civil War in his 1930 story "If Grant Had Been Drinking at Appomattox", which he accompanied with this very brief introduction: "Scribner's magazine is publishing a series of three articles: 'If Booth Had Missed Lincoln', 'If Lee Had Won the Battle of Gettysburg', and 'If Napoleon Had Escaped to America'. This is the fourth".
Another example of alternate history from this period (and arguably  the first that explicitly posited cross-time travel from one universe to another as anything more than a visionary experience) is H.G. Wells' Men Like Gods (1923) in which the London-based journalist Mr. Barnstable, along with two cars and their passengers, is mysteriously teleported into "another world", which the "Earthlings" call Utopia. Being far more advanced than Earth, Utopia is some 3000 years ahead of humanity in its development. Wells describes a multiverse of alternative worlds, complete with the paratime travel machines that would later become popular with American pulp writers. However, since his hero experiences only a single alternate world, the story is not very different from conventional alternate history. 
In the 1930s, alternate history moved into a new arena. The December 1933 issue of Astounding published Nat Schachner's "Ancestral Voices", which was quickly followed by Murray Leinster's " Sidewise in Time". While earlier alternate histories examined reasonably-straightforward divergences, Leinster attempted something completely different. In his "World gone mad", pieces of Earth traded places with their analogs from different timelines. The story follows Professor Minott and his students from a fictitious Robinson College as they wander through analogues of worlds that followed a different history.
A somewhat similar approach was taken by Robert A. Heinlein in his 1941 novelette Elsewhen in which a professor trains his mind to move his body across timelines. He then hypnotizes his students so that they can explore more of them. Eventually, each settles into the reality that is most suitable for him or her. Some of the worlds they visit are mundane, some are very odd, and others follow science fiction or fantasy conventions.
The period around World War II also saw the publication of the time travel novel Lest Darkness Fall by L. Sprague de Camp in which an American academic travels to Italy at the time of the Byzantine invasion of the Ostrogoths. De Camp's time traveler, Martin Padway, is depicted as making permanent historical changes and implicitly forming a new time branch, thereby making the work an alternate history.
In William Tenn's short story Brooklyn Project (1948), a tyrannical US Government brushes aside the warnings of scientists about the dangers of time travel and goes on with a planned experiment - with the result that minor changes to the prehistoric past cause Humanity to never have existed, its place taken by tentacled underwater intelligent creatures - who also have a tyrannical government which also insists on experimenting with time-travel. 
Time travel as the cause of a point of divergence (POD), which can denote either the bifurcation of a historical timeline or a simple replacement of the future that existed before the time-travelling event, has continued to be a popular theme. In Ward Moore's Bring the Jubilee, the protagonist lives in an alternate history in which the Confederacy has won the American Civil War. He travels backward through time and brings about a Union victory at the Battle of Gettysburg.
When a story's assumptions about the nature of time travel lead to the complete replacement of the visited time's future, rather than just the creation of an additional time line, the device of a "time patrol" is often used where guardians move through time to preserve the "correct" history.
A more recent example is Making History by Stephen Fry in which a time machine is used to alter history so that Adolf Hitler was never born. That ironically results in a more competent leader of Nazi Germany and results in the country's ascendancy and longevity in the altered timeline.
This section may contain material unrelated or insufficiently related to the topic of the article. (May 2019)
H.G. Wells' "cross-time" or "many universes" variant (see above) was fully developed by Murray Leinster in his 1934 short story "Sidewise in Time", in which sections of the Earth's surface begin changing places with their counterparts in alternate timelines.
Fredric Brown employed this subgenre to satirize the science fiction pulps and their adolescent readers—and fears of foreign invasion—in the classic What Mad Universe (1949). In Clifford D. Simak's Ring Around the Sun (1953), the hero ends up in an alternate earth of thick forests in which humanity never developed but a band of mutants is establishing a colony; the story line appears to frame the author's anxieties regarding McCarthyism and the Cold War.[ citation needed]
While many justifications for alternate histories involve a multiverse, the "many world" theory would naturally involve many worlds, in fact a continually exploding array of universes. In quantum theory, new worlds would proliferate with every quantum event, and even if the writer uses human decisions, every decision that could be made differently would result in a different timeline. A writer's fictional multiverse may, in fact, preclude some decisions as humanly impossible, as when, in Night Watch, Terry Pratchett depicts a character informing Vimes that while anything that can happen, has happened, nevertheless there is no history whatsoever in which Vimes has ever murdered his wife. When the writer explicitly maintains that all possible decisions are made in all possible ways, one possible conclusion is that the characters were neither brave, nor clever, nor skilled, but simply lucky enough to happen on the universe in which they did not choose the cowardly route, take the stupid action, fumble the crucial activity, etc.; few writers focus on this idea, although it has been explored in stories such as Larry Niven's story All the Myriad Ways, where the reality of all possible universes leads to an epidemic of suicide and crime because people conclude their choices have no moral import.
In any case, even if it is true that every possible outcome occurs in some world, it can still be argued that traits such as bravery and intelligence might still affect the relative frequency of worlds in which better or worse outcomes occurred (even if the total number of worlds with each type of outcome is infinite, it is still possible to assign a different measure to different infinite sets). The physicist David Deutsch, a strong advocate of the many-worlds interpretation of quantum mechanics, has argued along these lines, saying that "By making good choices, doing the right thing, we thicken the stack of universes in which versions of us live reasonable lives. When you succeed, all the copies of you who made the same decision succeed too. What you do for the better increases the portion of the multiverse where good things happen."  This view is perhaps somewhat too abstract to be explored directly in science fiction stories, but a few writers have tried, such as Greg Egan in his short story The Infinite Assassin, where an agent is trying to contain reality-scrambling "whirlpools" that form around users of a certain drug, and the agent is constantly trying to maximize the consistency of behavior among his alternate selves, attempting to compensate for events and thoughts he experiences, he guesses are of low measure relative to those experienced by most of his other selves.
Many writers—perhaps the majority—avoid the discussion entirely. In one novel of this type, H. Beam Piper's Lord Kalvan of Otherwhen, a Pennsylvania State Police officer, who knows how to make gunpowder, is transported from our world to an alternate universe where the recipe for gunpowder is a tightly held secret and saves a country that is about to be conquered by its neighbors. The paratime patrol members are warned against going into the timelines immediately surrounding it, where the country will be overrun, but the book never depicts the slaughter of the innocent thus entailed, remaining solely in the timeline where the country is saved.
The cross-time theme was further developed in the 1960s by Keith Laumer in the first three volumes of his Imperium sequence, which would be completed in Zone Yellow (1990). Piper's politically more sophisticated variant was adopted and adapted by Michael Kurland and Jack Chalker in the 1980s; Chalker's G.O.D. Inc trilogy (1987–89), featuring paratime detectives Sam and Brandy Horowitz, marks the first attempt at merging the paratime thriller with the police procedural.[ citation needed] Kurland's Perchance (1988), the first volume of the never-completed "Chronicles of Elsewhen", presents a multiverse of secretive cross-time societies that utilize a variety of means for cross-time travel, ranging from high-tech capsules to mutant powers. Harry Turtledove has launched the Crosstime Traffic series for teenagers featuring a variant of H. Beam Piper's paratime trading empire.
The concept of a cross-time version of a world war, involving rival paratime empires, was developed in Fritz Leiber's Change War series, starting with the Hugo Award winning The Big Time (1958); followed by Richard C. Meredith's Timeliner trilogy in the 1970s, Michael McCollum's A Greater Infinity (1982) and John Barnes' Timeline Wars trilogy in the 1990s.
Such "paratime" stories may include speculation that the laws of nature can vary from one universe to the next, providing a science fictional explanation—or veneer—for what is normally fantasy. Aaron Allston's Doc Sidhe and Sidhe Devil take place between our world, the "grim world" and an alternate "fair world" where the Sidhe retreated to. Although technology is clearly present in both worlds, and the "fair world" parallels our history, about fifty years out of step, there is functional magic in the fair world. Even with such explanation, the more explicitly the alternate world resembles a normal fantasy world, the more likely the story is to be labelled fantasy, as in Poul Anderson's "House Rule" and "Loser's Night". In both science fiction and fantasy, whether a given parallel universe is an alternate history may not be clear. The writer might allude to a POD only to explain the existence and make no use of the concept, or may present the universe without explanation of its existence.
Isaac Asimov's short story " What If—" (1952) is about a couple who can explore alternate realities by means of a television-like device. This idea can also be found in Asimov's novel The End of Eternity (1955), in which the "Eternals" can change the realities of the world, without people being aware of it. Poul Anderson's Time Patrol stories feature conflicts between forces intent on changing history and the Patrol who work to preserve it. One story, Delenda Est, describes a world in which Carthage triumphed over the Roman Republic. The Big Time, by Fritz Leiber, describes a Change War ranging across all of history.
Keith Laumer's Worlds of the Imperium is one of the earliest alternate history novels; it was published by Fantastic Stories of the Imagination in 1961, in magazine form, and reprinted by Ace Books in 1962 as one half of an Ace Double. Besides our world, Laumer describes a world ruled by an Imperial aristocracy formed by the merger of European empires, in which the American Revolution never happened, and a third world in post-war chaos ruled by the protagonist's doppelganger.
Philip K. Dick's novel, The Man in the High Castle (1962), is an alternate history in which Nazi Germany and Imperial Japan won World War II. This book contains an example of "alternate-alternate" history, in that one of its characters authored a book depicting a reality in which the Allies won the war, itself divergent from real-world history in several aspects. The several characters live within a divided United States, in which the Empire of Japan takes the Pacific states, governing them as a puppet, Nazi Germany takes the East Coast of the United States and parts of the Midwest, with the remnants of the old United States' government as the Neutral Zone, a buffer state between the two superpowers. The book has inspired an Amazon series of the same name.
Vladimir Nabokov's novel, Ada or Ardor: A Family Chronicle (1969), is a story of incest that takes place within an alternate North America settled in part by Czarist Russia and that borrows from Dick's idea of "alternate-alternate" history (the world of Nabokov's hero is wracked by rumors of a "counter-earth" that apparently is ours). Some critics[ who?] believe that the references to a counter-earth suggest that the world portrayed in Ada is a delusion in the mind of the hero (another favorite theme of Dick's novels[ citation needed]). Strikingly, the characters in Ada seem to acknowledge their own world as the copy or negative version, calling it "Anti-Terra", while its mythical twin is the real "Terra". Like history, science has followed a divergent path on Anti-Terra: it boasts all the same technology as our world, but all based on water instead of electricity; e.g., when a character in Ada makes a long-distance call, all the toilets in the house flush at once to provide hydraulic power.
Guido Morselli described the defeat of Italy (and subsequently France) in World War I in his novel, Past Conditional (1975; Contro-passato prossimo), wherein the static Alpine front line which divided Italy from Austria during that war collapses when the Germans and the Austrians forsake trench warfare and adopt blitzkrieg twenty years in advance.
Kingsley Amis set his novel, The Alteration (1976), in the 20th century, but major events in the Reformation did not take place, and Protestantism is limited to the breakaway Republic of New England. Martin Luther was reconciled to the Roman Catholic Church and later became Pope Germanian I.
In Nick Hancock and Chris England's 1997 book What Didn't Happen Next: An Alternative History of Football it is suggested that, had Gordon Banks been fit to play in the 1970 FIFA World Cup quarter-final, there would have been no Thatcherism and the post-war consensus would have continued indefinitely. [ page needed]
Kim Stanley Robinson's novel, The Years of Rice and Salt (2002), starts at the point of divergence with Timur turning his army away from Europe, and the Black Death has killed 99% of Europe's population, instead of only a third. Robinson explores world history from that point in AD 1405 (807 AH) to about AD 2045 (1467 AH). Rather than following the great man theory of history, focusing on leaders, wars, and major events, Robinson writes more about social history, similar to the Annales School of history theory and Marxist historiography, focusing on the lives of ordinary people living in their time and place.
Philip Roth's novel, The Plot Against America (2004), looks at an America where Franklin D. Roosevelt is defeated in 1940 in his bid for a third term as President of the United States, and Charles Lindbergh is elected, leading to a US that features increasing fascism and anti-Semitism.
Michael Chabon, occasionally an author of speculative fiction, contributed to the genre with his novel The Yiddish Policemen's Union (2007), which explores a world in which the State of Israel was destroyed in its infancy and many of the world's Jews instead live in a small strip of Alaska set aside by the US government for Jewish settlement. The story follows a Jewish detective solving a murder case in the Yiddish-speaking semi-autonomous city state of Sitka. Stylistically, Chabon borrows heavily from the noir and detective fiction genres, while exploring social issues related to Jewish history and culture. Apart from the alternate history of the Jews and Israel, Chabon also plays with other common tropes of alternate history fiction; in the book, Germany actually loses the war even harder than they did in reality, getting hit with a nuclear bomb instead of just simply losing a ground war (subverting the common "what if Germany won WWII?" trope).
The late 1980s and the 1990s saw a boom in popular-fiction versions of alternate history, fueled by the emergence of the prolific alternate history author Harry Turtledove, as well as the development of the steampunk genre and two series of anthologies—the What Might Have Been series edited by Gregory Benford and the Alternate ... series edited by Mike Resnick. This period also saw alternate history works by S. M. Stirling, Kim Stanley Robinson, Harry Harrison, Howard Waldrop, Peter Tieryas,  and others.
In 1986, a sixteen-part epic comic book series called Captain Confederacy began examining a world where the Confederate States of America won the American Civil War. In the series, the Captain and others heroes are staged government propaganda events featuring the feats of these superheroes. 
Since the late 1990s, Harry Turtledove has been the most prolific practitioner of alternate history and has been given the title "Master of Alternate History" by some.  His books include those of Timeline 191 (a.k.a. Southern Victory, also known as TL-191), in which, while the Confederate States of America won the American Civil War, the Union and Imperial Germany defeat the Entente Powers in the two "Great War"s of the 1910s and 1940s (with a Nazi-esque Confederate government attempting to exterminate its Black population), and the Worldwar series, in which aliens invaded Earth during World War II. Other stories by Turtledove include A Different Flesh, in which America was not colonized from Asia during the last ice age; In the Presence of Mine Enemies, in which the Nazis won World War II; and Ruled Britannia, in which the Spanish Armada succeeded in conquering England in the Elizabethan era, with William Shakespeare being given the task of writing the play that will motivate the Britons to rise up against their Spanish conquerors. He also co-authored a book with actor Richard Dreyfuss, The Two Georges, in which the United Kingdom retained the American colonies, with George Washington and King George III making peace. He did a two-volume series in which the Japanese not only bombed Pearl Harbor but also invaded and occupied the Hawaiian Islands.
Perhaps the most incessantly explored theme in popular alternate history focuses on worlds in which the Nazis won World War Two. In some versions, the Nazis and/or Axis Powers conquer the entire world; in others, they conquer most of the world but a "Fortress America" exists under siege; while in others, there is a Nazi/Japanese Cold War comparable to the US/Soviet equivalent in 'our' timeline. Fatherland (1992), by Robert Harris, is set in Europe following the Nazi victory. The novel Dominion by C.J. Sansom (2012) is similar in concept but is set in England, with Churchill the leader of an anti-German Resistance and other historic persons in various fictional roles.  In the Mecha Samurai Empire series (2016), Peter Tieryas focuses on the Asian-American side of the alternate history, exploring an America ruled by the Japanese Empire while integrating elements of Asian pop culture like mechas and videogames. 
Several writers have posited points of departure for such a world but then have injected time splitters from the future or paratime travel, for instance James P. Hogan's The Proteus Operation. Norman Spinrad wrote The Iron Dream in 1972, which is intended to be a science fiction novel written by Adolf Hitler after fleeing from Europe to North America in the 1920s.
In Jo Walton's "Small Change" series, the United Kingdom made peace with Hitler before the involvement of the United States in World War II, and slowly collapses due to severe economic depression. Former House Speaker Newt Gingrich and William R. Forstchen have written a novel, 1945, in which the US defeated Japan but not Germany in World War II, resulting in a Cold War with Germany rather than the Soviet Union. Gingrich and Forstchen neglected to write the promised sequel; instead, they wrote a trilogy about the American Civil War, starting with Gettysburg: A Novel of the Civil War, in which the Confederates win a victory at the Battle of Gettysburg - however, after Lincoln responds by bringing Grant and his forces to the eastern theater, the Army of Northern Virginia is soon trapped and destroyed in Maryland, and the war ends within weeks.
While World War II has been a common Point of Divergence in alternate history literature, several works have been based on other points of divergence. For example, Martin Cruz Smith, in his first novel, posited an independent American Indian nation following the defeat of Custer in The Indians Won (1970).  Beginning with The Probability Broach in 1980, L. Neil Smith wrote several novels that postulated the disintegration of the US Federal Government after Albert Gallatin joins the Whiskey Rebellion in 1794 and eventually leads to the creation of a libertarian utopia.  In the 2022 novel Poutine and Gin by Steve Rhinelander, the point of divergence is the Battle of the Plains of Abraham of the French and Indian War. That novel is a mystery set in 1940 of that time line.
A recent time traveling splitter variant involves entire communities being shifted elsewhere to become the unwitting creators of new time branches. These communities are transported from the present (or the near-future) to the past or to another time-line via a natural disaster, the action of technologically advanced aliens, or a human experiment gone wrong. S. M. Stirling wrote the Island in the Sea of Time trilogy, in which Nantucket Island and all its modern inhabitants are transported to Bronze Age times to become the world's first superpower. In Eric Flint's 1632 series, a small town in West Virginia is transported to 17th century central Europe and drastically changes the course of the Thirty Years' War, which was then underway. John Birmingham's Axis of Time trilogy deals with the culture shock when a United Nations naval task force from 2021 finds itself back in 1942 helping the Allies against the Empire of Japan and the Germans (and doing almost as much harm as good in spite of its advanced weapons). The series also explores the cultural impacts of people with 2021 ideals interacting with 1940s culture. Similarly, Robert Charles Wilson's Mysterium depicts a failed US government experiment which transports a small American town into an alternative version of the US run by believers in a form of Christianity known as Gnosticism, who are engaged in a bitter war with the "Spanish" in Mexico (the chief scientist at the laboratory where the experiment occurred is described as a Gnostic, and references to Christian Gnosticism appear repeatedly in the book).  In Time for Patriots by retired astronomer Thomas Wm. Hamilton ( 4897 Tomhamilton) a town and military academy on Long Island are transported back to 1770, where they shorten the American Revolution, rewrite the Constitution, prolong Mozart's life, battle Barbary pirates, and have other adventures.
Although not dealing in physical time travel, in his alt-history novel Marx Returns, Jason Barker introduces anachronisms into the life and times of Karl Marx, such as when his wife Jenny sings a verse from the Sex Pistols's song " Anarchy in the U.K.", or in the games of chess she plays with the Marxes' housekeeper Helene Demuth, which on one occasion involves a Caro–Kann Defence.  In her review of the novel, Nina Power writes of "Jenny’s 'utopian' desire for an end to time", an attitude which, according to Power, is inspired by her husband's co-authored book The German Ideology. However, in keeping with the novel's anachronisms, the latter was not published until 1932.  By contrast, the novel's timeline ends in 1871.
In the 2022 novel Hydrogen Wars: Atomic Sunrise by R.M. Christianson a small change in post-war Japanese history leads to the election of General Douglas MacArthur as President of the United States. This minor change ultimately leads to all-out atomic war between the major Cold War powers. 
Many works of straight fantasy and science fantasy take place in historical settings, though with the addition of, for example, magic or mythological beasts. Some present a secret history in which the modern day world no longer believes that these elements ever existed. Many ambiguous alternate/secret histories are set in Renaissance or pre-Renaissance times, and may explicitly include a "retreat" from the world, which would explain the current absence of such phenomena. Other stories make plan a divergence of some kind.
In Poul Anderson's Three Hearts and Three Lions in which the Matter of France is history and the fairy folk are real and powerful. The same author's A Midsummer Tempest, occurs in a world in which the plays of William Shakespeare (called here "the Great Historian"), presented the literal truth in every instance. The novel itself takes place in the era of Oliver Cromwell and Charles I. Here, the English Civil War had a different outcome, and the Industrial Revolution has occurred early.
Randall Garrett's " Lord Darcy" series presents a point of divergence: a monk systemizes magic rather than science, so the use of foxglove to treat heart disease is regarded as superstition. Another point of divergence occurs in 1199, when Richard the Lionheart survives the Siege of Chaluz and returns to England and makes the Angevin Empire so strong that it survives into the 20th century.
Jonathan Strange & Mr Norrell by Susanna Clarke takes place in an England where a separate Kingdom ruled by the Raven King and founded on magic existed in Northumbria for over 300 years. In Patricia Wrede's Regency fantasies, Great Britain has a Royal Society of Wizards.
The Tales of Alvin Maker series by Orson Scott Card (a parallel to the life of Joseph Smith, founder of the Latter Day Saint movement) takes place in an alternate America, beginning in the early 19th century. Prior to that time, a POD occurred: England, under the rule of Oliver Cromwell, had banished "makers", or anyone else demonstrating "knacks" (an ability to perform seemingly supernatural feats) to the North American continent. Thus the early American colonists embraced as perfectly ordinary these gifts, and counted on them as a part of their daily lives. The political division of the continent is considerably altered, with two large English colonies bookending a smaller "American" nation, one aligned with England, and the other governed by exiled Cavaliers. Actual historical figures are seen in a much different light: Ben Franklin is revered as the continent's finest "maker", George Washington was executed after being captured, and "Tom" Jefferson is the first president of "Appalachia", the result of a compromise between the Continentals and the British Crown.[ citation needed]
On the other hand, when the "Old Ones" (fairies) still manifest themselves in England in Keith Roberts's Pavane, which takes place in a technologically backward world after a Spanish assassination of Elizabeth I allowed the Spanish Armada to conquer England, the possibility that the fairies were real but retreated from modern advances makes the POD possible: the fairies really were present all along, in a secret history.
Again, in the English Renaissance fantasy Armor of Light by Melissa Scott and Lisa A. Barnett, the magic used in the book, by Dr. John Dee and others, actually was practiced in the Renaissance; positing a secret history of effective magic makes this an alternate history with a point of departure. Sir Philip Sidney survives the Battle of Zutphen in 1586, and shortly thereafter saving the life of Christopher Marlowe.
When the magical version of our world's history is set in contemporary times, the distinction becomes clear between alternate history on the one hand and contemporary fantasy, using in effect a form of secret history (as when Josepha Sherman's Son of Darkness has an elf living in New York City, in disguise) on the other. In works such as Robert A. Heinlein's Magic, Incorporated where a construction company can use magic to rig up stands at a sporting event and Poul Anderson's Operation Chaos and its sequel Operation Luna, where djinns are serious weapons of war—with atomic bombs—the use of magic throughout the United States and other modern countries makes it clear that this is not secret history—although references in Operation Chaos to degaussing the effects of cold iron make it possible that it is the result of a POD. The sequel clarifies this as the result of a collaboration of Einstein and Planck in 1901, resulting in the theory of "rhea tics". Henry Moseley applies this theory to "degauss the effects of cold iron and release the goetic forces." This results in the suppression of ferromagnetism and the re-emergence of magic and magical creatures.
Alternate history shades off into other fantasy subgenres when the use of actual, though altered, history and geography decreases, although a culture may still be clearly the original source; Barry Hughart's Bridge of Birds and its sequels take place in a fantasy world, albeit one clearly based on China, and with allusions to actual Chinese history, such as the Empress Wu. Richard Garfinkle's Celestial Matters incorporates ancient Chinese physics and Greek Aristotelian physics, using them as if factual.
Alternate history has long been a staple of Japanese speculative fiction with such authors as Futaro Yamada and Ryō Hanmura writing novels set in recognizable historical settings with added supernatural or science fiction elements. Ryō Hanmura's 1973 Musubi no Yama Hiroku which recreated 400 years of Japan's history from the perspective of a secret magical family with psychic abilities. The novel has since come to be recognized as a masterpiece of Japanese speculative fiction.  Twelve years later, author Hiroshi Aramata wrote the groundbreaking Teito Monogatari which reimagined the history of Tokyo across the 20th century in a world heavily influenced by the supernatural. 
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The TV show Sliders explores different possible alternate realities by having the protagonist "slide" into different parallel dimensions of the same planet Earth. Another TV show Motherland: Fort Salem explores a female-dominated world in which witchcraft is real. Its world diverged from our timeline when the Salem witch trials are resolved by an agreement between witches and ungifted humans.
The TV show The Man in the High Castle is an adaptation of the novel with the same name that ran for four seasons.
For All Mankind depicts an alternate timeline in which the Soviet crewed lunar program successfully lands on the Moon before the US Apollo program, resulting in a continued and intensified Space Race.
Fans of alternate history have made use of the internet from a very early point to showcase their own works and provide useful tools for those fans searching for anything alternate history, first in mailing lists and usenet groups, later in web databases and forums. The "Usenet Alternate History List" was first posted on 11 April 1991, to the Usenet newsgroup rec.arts.sf-lovers. In May 1995, the dedicated newsgroup soc.history.what-if was created for showcasing and discussing alternate histories.  Its prominence declined with the general migration from unmoderated usenet to moderated web forums, most prominently AlternateHistory.com, the self-described "largest gathering of alternate history fans on the internet" with over 10,000 active members.  
In addition to these discussion forums, in 1997 Uchronia: The Alternate History List was created as an online repository, now containing over 2,900 alternate history novels, stories, essays, and other printed materials in several different languages. Uchronia was selected as the Sci Fi Channel's "Sci Fi Site of the Week" twice.