Answer:
Nuclear weaponry
Step-by-step explanation:
The entire premise of the cold war is a war that could go hot at any moment, yet didn't due to one thing: M.A.D. mutually assured destruction. MAD asserts that when two powers have weaponry or otherwise the ability to decimate the other, one power attacking the other will result in being attacked in the same way, causing both sides to lose. Thus, both sides of the Cold War were competing to try and have more and better nuclear weapons than the other side.