In 1970, a Russian Atomic Submarine Sank. It Was Armed with Nuclear Weapons.
The Soviet Navy (which did not have much interest in the strategic mission at that point) reconfigured the 627 class for a more conventional anti-ship role. Despite their noisiness, the Novembers had the range to threaten NATO surface vessels, especially transport convoys. A small number of nuclear torpedoes (configured with smaller warheads compatible with conventional torpedoes) could wreak havoc on such a convoy, despite the likely loss of the sub to any surviving escorts.