The shortest recorded war in history that lasted 38 minutes was between which countries?

The Anglo-Zanzibar War was a military conflict fought between the United Kingdom and the Zanzibar Sultanate on 27 August 1896. The conflict lasted between 38 and 45 minutes, marking it as the shortest recorded war in history. The immediate 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.

The British authorities preferred Hamoud bin Mohammed. In the agreement of 14 June 1890 instituting a British protectorate over Zanzibar, a candidate for accession to the sultanate should obtain the permission of the British consul, and Khalid had not fulfilled this requirement. The British considered this a casus belli (act or event that provokes or is used to justify war) and sent an ultimatum to Khalid demanding that he order his forces to stand down and 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 (EAT) 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.

The sultan's forces sustained roughly 500 casualties, while only one British sailor was injured. Sultan Khalid received asylum in the German consulate before escaping to German East Africa. The war marked the end of the Zanzibar Sultanate as a sovereign state and the start of a period of heavy British influence.