Skybird, the Sovet Union did not act predictably.
The Cuban missile crisis is one big proof that invalidates your argument.
As well as the 1983 Able Archer Nato exercise that was interpreted by the Soviets as a prelude to war.
If the cold war finished without hundreds of giant mushrooms over our heads is mostly because of luck.
Many people conviniently have forgotten how close the cold war came to being hot.