The assumption of a no first use nuclear strategy during the cold war, with the caveat that NATO would use nuclear weapons in WW3 in order to scare soviet planners into leaving the west alone, seems to have arisen after the 1950s. However, nuclear escalation was present as a strategy by policy planners in the US during the Korean war and calmer heads prevailed. Did the fear of either side pushing their luck prevent open conflict with the west from China and to a lesser extant the Soviet Union after this conflict?
Why the down votes? Basically, why did the korean war not end in nuclear conflagration, when WW3 never happened because of MAD. My theory is that the korean war solidified the danger of atomic weapons based on the inability of either side to achieve a strategic victory without restarting to extreme measures.