As the new Victors and Vulcans became available, Valiants became surplus to the planned V force of 144 aircraft. It was proposed that 24 Valiants could replace 64 Canberra bombers. This represented a numerical reduction in the force available to SACEUR, but an improvement in capability due to the Valiants' all-weather strike capacity. The decision was taken by the Air Council on 15 May 1958. The first squadron to be assigned was No. 207 Squadron, on 1 January 1960. It was followed by No. 49 Squadron on 1 July, and No. 148 on 13 July. No. 49 Squadron moved to RAF Marham so that all three squadrons were concentrated there. They were each equipped with two Mark 28 nuclear bombs provided by Project E. The three TBF squadrons eventually became the only Valiant bomber squadrons as all the others were disbanded or converted to tanker or strategic reconnaissance roles. They adopted SACEUR's Quick Reaction Alert, under which arrangements were made so that three armed aircraft were always ready to scramble within 15 minutes. They were also the first V bombers to adopt a low-level strike role, with their white paintwork replaced by green camouflage. During the Cuban Missile Crisis, each V force squadron kept one fully armed aircraft and crew at 15 minutes' readiness. By 1963, the RAF was convinced that, to have any chance of survival, the V bombers would have to attack at low level. At altitudes below , radar was less effective due to ground-generated clutter. The three Vulcan B.1A squadrons at RAF Waddington and the four Victor B.1A squadrons at RAF Honington and RAF Cottesmore were ordered to switch to low-level operations in March 1963. The Vulcan B.2 and Victor B.2 squadrons followed on 1 May 1964. A sign of the new doctrine was the replacement of their white paintwork with green camouflage on their upper surfaces, starting with Vulcan XH505 on 24 March 1964. They were also outfitted with new ECMs, ground positioning equipment and terrain-following radar. Tests performed in the UK and at Woomera demonstrated that Blue Steel could be launched from low level. The Yellow Sun Mark 2 free-fall bomb was a different story, and V bombers equipped with it would have had to climb to medium altitude to release it. A new bomb, the WE.177 was developed. Deliveries of the WE.177B commenced in September 1966. Through Project E and the introduction of