The shortest war in history was between Britain and Zanzibar on August 27, 1896 - Apparently.
On that day, Zanzibar surrendered after just 38 minutes of fighting, making it the shortest war in recorded history. The war began when the British ship HMS Philomel arrived in Zanzibar Harbor, delivering an ultimatum to the Zanzibari forces, which they ignored. The British then opened fire, and after a brief but intense bombardment, the Zanzibari forces retreated, and Zanzibar surrendered, ceding control to Britain. This bizarre and brief conflict is still recognized by the Guinness World Records as the shortest war in history.