The term 'V bomber' was used for RAF aircraft (Vickers Valiant, Handley Page Victor and Avro Vulcan) during the 1950s and 1960s that comprised the UK's strategic nuclear strike force known officially as the V-Force. The V-Force reached its peak in June 1964, with 50 Valiants, 70 Vulcans and 39 Victors in service. During the Cuban Missile Crisis in October 1962, RAF V-Force bombers were brought to readiness on 15-minute notice with the aircraft armed and crews ready beside them.The RAF's V-Force remained Britain's nuclear deterrent up 1969 when the strategic role was assumed by the Royal Navy with its Polaris nuclear submarines.