The shortest war in recorded history was between Zanzibar and England in 1896. Zanzibar surrendered after 38 minutes, though the official history says that the war began at 9.00am on the 27th of August with the expiry of an ultimatum regarding the succession of the Sultan of Zanzibar. The British did not want Sultan Khalid bin Barghash to succeed Sultan Hamad bin Thuwaini as ruler preferring Hamud bin Muhammed, who was somewhat more pro British. Though the history also suggests Khalid bin Bargash possibly assassinated the previous Sultan, so might not have been all that nice a chap. Of course he might Just have been a Nationalist, who didn’t see why the British should be consulted about who should be Sultan, as agreed in a treaty of 1886.
The British had three cruisers, two gunships, 150 marines and sailors, and 900 Zanzibaris in the harbour and bombardment of the Sultans Palace defended by about 2800 Zanzibaris, began at 9.02. Three Zanzibari vessels including the Zanzibari Royal Yacht, attacked the British Ships and were promptly sunk. The bombardment of the Palace continued setting fire to it, which was reportedly responsible for most of the 500 casualties among the Defenders.
At 9.40 the Sultans flag was either shot down or cut down, this was interpreted as a surrender, and the ‘war’ was over, a British Petty Officer was severely injured but later recovered. The deposed Sultan took refuge in the German Consulate and later left on a German warship for German east Africa.
Although not the origin of the term, this is possibly the best example of what happens when someone fails to respond to Gunboat Diplomacy.