Originally the bombing role was to have been carried out at high altitude, but following the shooting down in 1960 of the Lockheed U-2 flown by Gary Powers by an early Soviet SA-2 Guideline missile, the SAM threat caused bomber squadrons to train for low-level attack as a means of avoiding radar detection when flying within hostile airspace. They were repainted in grey/green camouflage with normal markings, replacing their anti-flash white scheme. By 1963, four Valiant squadrons (49, 148, 207 and 214) had been assigned to SACEUR in the low-level tactical bombing role. By this point, there had been a noticeable decline in flying rates for the type.