The thinking has always been that we need a triad of nuclear delivery systems, partially for deterrence and partially as a hedge against future technology. Subm

The thinking has always been that we need a triad of nuclear delivery systems, partially for deterrence and partially as a hedge against future technology. Submarines are survivable today, but who knows what new detection system a brilliant Chinese scientist might invent tomorrow? And SLBMs can't really hold deeply buried bunkers at risk, like the ones heavily used in North Korea and Iran. Hitting those takes an air delivered "bunker buster" nuke.