There is no real defense against a nuclear warhead blowing up within a few hundred yards of a ship. That said there will never be another nuclear war if both sides have them. The last 70 years have proven that. Hell, we didn’t nuke Korea or Vietnam and there wasn’t threat of retaliation.
“... there will never be another nuclear war if both sides have them.”
Excepting Li’l Kimmy NOKO and the Mad Mullahs ...