Editing Alternate history (section)

====Time travel to create historical divergences====
{{original research|section|date=October 2023}}
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.<ref>{{cite web |last1=Jonas |first1=Gerald |title=William Tenn, Science Fiction Author, Is Dead at 89 |url=https://www.nytimes.com/2010/02/14/books/14tenn.html |archive-url=https://ghostarchive.org/archive/20220101/https://www.nytimes.com/2010/02/14/books/14tenn.html |archive-date=1 January 2022 |url-access=limited |website=[[The New York Times]] |accessdate=5 April 2020 |date=13 February 2010}}{{cbignore}}</ref>

In [[Ray Bradbury]]'s classic short story "[[A Sound of Thunder]]" (1952) a group of hunters travel to the [[Late Cretaceous]] to hunt dinosaurs whose death would not be considered consequential as they are about to die a natural death within two minutes of the encounter. To minimize risking  changes history they are told to stay on a levitating antigravity path that touches nothing. However one of the hunters stumbles off the path, inadvertently crushing a butterfly. When the group returns they find that history became significantly harsher and a fascist is now President.<ref>{{cite book |editor-last=Vandermeer |editor-first=Ann and Jeff |date=Mar 18, 2014 |title=The Time Travelers Almanac  |location= |publisher=TORDOTCOM |page= |isbn=978-0765374240 }}</ref>

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]]'' (1953), 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 (novel)|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.