Operation Boris was a British plan for military intervention in Zanzibar following the 1964 revolution. It was devised around 20 February to be used if the radical left-wing Umma Party attempted to take power. It replaced the earlier sea-based Operation Parthenon with a parachute assault launched from Kenya. However the operation was not required and was jeopardised by the lack of co-operation from the Kenyan government and populace for an attack on Zanzibar. Boris was replaced by Operation Finery, an amphibious helicopter assault, on 9 April 1964.