What caused the Mutually Assured Destruction ?

MAD was just a broad concept like the "Global War on Terror". It wasn't an "Official" policy with military manuals and what not. It just meant that if Russia attacked America we would retaliate and both of us would be totally annihilated and vice versa, thus the reasoning went that no one would attack the other because that meant they would be destroyed also. That's why Submarines played such an important part in the Cold War because you could basically have a couple dozen or so nuclear missiles directly off the others coast in a sub that no one can find. You could have attacked and wiped the Other country out before they had time to respond. That's why so many Cold War resources were spent tracking Russian Subs and why we sent so many of our subs to the North Atlantic. The reason we fell into that whole scenario in the first place was because a bunch of the fathers of the "bomb" were Communists and had very little oversight so it was very easy for Russia to acquire the ability to build nukes immediately after WW2. Both Russia and the US wanted to spread there influence throughout europe and elsewhere so we wound up competing and due to our radically different Governmental philosophies we were just natural enemies.