The Air Force countered that having a variety of platforms complicated the defense; if the Soviets built an effective anti-ballistic missile system of some sort, the ICBM and SLBM fleet might be rendered useless, while the bombers would remain. This became the nuclear triad concept, which survives into the present. Although this argument was successful, the number of manned bombers has been repeatedly cut and the deterrent role increasingly passed to missiles.
