Comment by betterunix2

It is OTP, that is not a secret. The secret is not how the orders are being communicated, it is the actual meaning of the orders (e.g. the targeting pattern) and certain strategically significant details about how a launch order would be executed (e.g. if only one pair of launch keys is turned there is a timeout during which another missileer crew can cancel the launch; the length of that timeout is secret). During the cold war nuclear strategy was the subject of extensive research by both the US and the USSR, which is why both sides wound up pursuing essentially the same strategy.

(China is interesting because strictly speaking they follow a theoretically suboptimal strategy -- they keep their ICBMs in an unarmed configuration and would "absorb the blow" of a surprise nuclear first strike. The US and RF follow the theoretically optimal "launch on warning" strategy, which requires ICBMs that are always armed and ready to launch within minutes.)