| Cause | War |
| Caesar Crosses the Rubicon | |
| Confederate forces fire at Fort Sumter | |
| Germany invades Poland | |
| Franz Ferdinand is shot | |
| A shot is fired at Lexington Green | |
| Defenestration of Prague | |
| USS Maine explodes | |
| Texas is annexed | |
| | Cause | War |
| Council of Clermont | |
| Louis XIV supports his grandson's claim to the throne of Spain | |
| Frederick the Great invades Silesia | |
| Rome tries to take Sicily from Carthage | |
| Athens supports an Ionian revolt | |
| Monarchical nations of Europe try to reinstall the French monarchy | |
| Japanese and Chinese troops have a skirmish at the Marco Polo Bridge | |
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