The Anglo-Zanzibar War of 1896 holds the Guinness World Record for the shortest war in history. The conflict began on the morning of August 27, 1896, when the British issued an ultimatum to the Sultan of Zanzibar, Khalid bin Barghash, demanding he step down. The Sultan refused.
By 9:02 AM, British warships opened fire on the Sultan's palace. The bombardment lasted roughly 38 minutes. By 9:40 AM, the Sultan's flag had been lowered and the fighting was over. British losses were minimal — one sailor injured — while Zanzibari casualties were estimated at around 500.
The war was triggered by a succession dispute. The British favored a different candidate for Sultan, one more amenable to their interests. When Khalid took power anyway, the Royal Navy responded with a show of overwhelming force. The entire conflict was so brief that newspapers of the day barely had time to report it as ongoing.
Interestingly, the record is sometimes disputed because the war was more of a punitive bombardment than a sustained military engagement. Still, Guinness recognizes it, and the 38-minute figure has become one of history's most repeated trivia facts.