What was the shortest war in history?

The Anglo-Zanzibar War was a military conflict fought between the UK and the Zanzibar Sultanate. The conflict lasted around 38 minutes, marking it as the shortest war in history. The cause of the war was the death of the pro-British Sultan Hamad bin Thuwaini on 25 August 1896 and the subsequent succession of Sultan Khalid bin Barghash. In accordance with a treaty signed in 1886, a condition for accession to the sultanate was that the candidate obtain the permission of the British consul, and Khalid had not fulfilled this requirement. The British considered this a casus belli and sent an ultimatum demanding that Khalid leave the palace. In response, Khalid called up his palace guard and barricaded himself inside the palace.

The ultimatum expired at 09:00 East Africa Time on 27 August, by which time the British had gathered three cruisers, two gunboats, 150 marines and sailors, and 900 Zanzibaris in the harbour area. Around 2,800 Zanzibaris defended the palace. The defenders had several artillery pieces and machine guns, which were set in front of the palace sighted at the British ships. A bombardment opened at 09:02 set the palace on fire and disabled the defending artillery -- see picture. A small naval action took place and some shots were fired ineffectually at the pro-British Zanzibari troops as they approached the palace. The flag at the palace was shot down and fire ceased at 09:40.