Why breaching Soviet SSBN bastions risks nuclear escalation

What would happen if NATO tried to force its way into Soviet ballistic-missile-submarine bastions?

It would trigger a large anti-submarine battle and might push Soviet leaders toward early nuclear use if they believed their surviving deterrent was about to be destroyed.

NATO attack submarines could penetrate Soviet defensive zones, but they would face layered submarines, surface ships, aircraft, mines, and fixed sensors. Soviet Kiev- and Slava-type surface forces could draw attention while the ballistic-missile submarines dispersed or prepared to fire. Because the targets formed part of the Soviet second-strike force, a successful conventional attack could look like the opening of nuclear disarmament. The operational need to find and destroy the submarines quickly would therefore collide with an extreme escalation risk.