Here's a fun story, it's 1990, you're on the bridge of the aircraft carrier USS Ranger (CV-61) in the Persian Gulf when two B-52s request to do a flyby, which gets approved. The pilots call out their distances as they get closer, and yet nobody on the bridge can see them. Finally people spot plumes of sea spray behind the jets as they come in for a flyby at below deck height. There are some amazing pictures of it.

By the late Cold War a variety of techniques had been developed to increase the potential survivability of strategic bombers. Of course, in the US strategic bombers had already been enshrined as part of the "nuclear triad" since the '50s/'60s and there was a level of departmental territoriality and pride that made it difficult to unwind that distribution regardless of the objective relative utility of each part of the triad (with the bomber based portion definitely becoming less and less sure-footed from the '70s onward). However, technology and techniques advanced along and kept Strategic Air Command "in the game" through the end of the Cold War. One of the key techniques that became hugely advantageous pretty early on (starting in the 1960s) was the ability to fly at very low levels. This "nap of the Earth" flying makes it possible to avoid enemy radar systems (rendering SAM sites ineffective as well) and leaves a plane vulnerable mostly only to interceptor aircraft. On top of this there were a whole coordinated series of tactics designed to increase the likelihood of successfully penetrating Soviet air defenses. For example, bombers could carry land attack cruise missiles (such as the Hound Dog, the AGM-69, the AGM-86, etc.) which could be launched as the planes entered enemy airspace and would travel hundreds of miles to take out air defense targets including airfields and SAM sites with their own nuclear warheads. On top of that bombers were equipped with electronic countermeasures packages that could jam enemy radar and reduce the chance of interception before hitting their targets.

Even so, most B-52 pilots didn't fool themselves into thinking that their nuclear attack missions were anything but one way trips with only a chance of "success" at hitting their targets and almost no chance of returning alive. But, their chances of the entire bomber fleet being able to deliver a devastating blow were actually pretty high, even if each individual mission was less assured.

By the very late Cold War the venerable B-52 was pretty well understood to be pushing viability for its role, which is why other bombers were being built as replacements. First the B-1 as a harder to intercept long-range bomber then the B-2 "stealth bomber" (which began development in the late '70s and managed to squeak into a first flight just months before the Berlin Wall fell).