These are some historical turning points used as a basis for alternative histories in various novels and stories that I'm familiar with. Obviously, there are many that I'm not familiar with, so these are a very personal selection.
They're all historical events that could plausibly have gone differently with a change in luck. In some cases, time-travellers are involved; but I've excluded stories such as Harry Turtledove's Guns of the South, in which there was no historical turning point: the time-travellers created one by their own efforts.
| Date | Turning point | Alternative history found in |
|---|---|---|
| June 323 BC | Alexander the Great survives whatever killed him at the age of 32 in our history (heavy drinking, illness, and/or poisoning), and lives on until 280 BC. | S. M. Stirling's novel Conquistador |
| November 218 BC | Publius Cornelius Scipio and his son are both killed at the Battle of Ticinus in northern Italy, after which Carthage wins the Second Punic War and Rome is destroyed. | Poul Anderson's story "Delenda Est" |
| March/April 1199 | King Richard I of England survives being hit by a crossbow bolt in France, and lives on until 1219, succeeded by his nephew Arthur. Their dynasty reigns over a growing Anglo-French Empire. | Randall Garrett's Lord Darcy stories |
| 16 July 1212 | The Muslim army of Muhammad al-Nasir wins the battle of Las Navas de Tolosa, and the Christian reconquest of Spain fails. | Harry Harrison's novel A Transatlantic Tunnel, Hurrah! |
| 31 August 1422 | King Henry V of England (aged 35) does not die suddenly and unexpectedly. He therefore becomes King of France (as well as England) after the death of Charles VI of France in October, as agreed in the Treaty of Troyes (1420). Will he be able to keep both kingdoms? | I haven't seen a story about this turning point; I wonder why not. |
| May 1553 | King Edward VI of England makes a complete recovery from his illness, lives a full life, and is succeeded by his son, maintaining the Tudor dynasty. Neither Mary nor Elizabeth ever reigns. | I haven't seen a story about this turning point; I wonder why not. |
| July 1588 | The Spanish Armada succeeds in its mission, Elizabeth is a prisoner in the Tower of London, and the daughter of the Spanish king is installed as Queen of England—now a Catholic country. | Harry Turtledove's novel Ruled Britannia |
| 31 December 1775 | Benedict Arnold is killed in the failed attack on Quebec (instead of being wounded). With Arnold gone, the British win the Battles of Saratoga, and the American Revolution fails. Then the French King Louis XVI shows more spirit and defeats the French Revolution. | H. Beam Piper's story "He Walked Around the Horses" |
| late 1780s | The three minor Pennamite Wars between Connecticut and Pennsylvania (1769–1784) are followed by a fourth, in which George Washington tries to intervene and is killed. The United States break up and the separate states all go on fighting each other intermittently. | Michael Flynn's story "The Forest of Time" |
| 6 April 1862 | Confederate General Albert Sidney Johnston is not hit by a bullet, survives the Battle of Shiloh, and wins it. | I haven't seen a story about this turning point; I wonder why not. |
| 10 September 1862 | Robert E. Lee's Special Order 191 is not picked up by his enemies, so there's no Battle of Antietam. Instead the Confederates win the Battle of Camp Hill, then take Philadelphia and Kentucky, and win the war. | Harry Turtledove's novel How Few Remain, of which I've read only the synopsis! |
| 1 July 1863 | A Confederate brigade occupies Little Round Top at the start of the Battle of Gettysburg, enabling the Confederates to win the battle and then the war. | Ward Moore's novel Bring the Jubilee |
| 3 October 1878 | A number of comets or cometary fragments strike Europe and North America, killing many people and causing several years of very cold weather. The European and North American countries don't survive the winter years, but some survivors manage to emigrate, and the British Empire continues, ruled from Delhi. | S. M. Stirling's novel The Peshawar Lancers |
| 25 May 1912 | US President William Howard Taft dies of a heart attack, and Theodore Roosevelt retakes the presidency in November, beating Woodrow Wilson. | S. M. Stirling's novel Black Chamber |