There is also something to be said for convincing your enemy to build obsolete weaponry that is more expensive to build than the obsolete weaponry they were alr

There is also something to be said for convincing your enemy to build obsolete weaponry that is more expensive to build than the obsolete weaponry they were already building. If you have reasonable certainty there won't be a hot war, winning a cold war is a matter of having a stronger economy and better logistics. You can leak older missile tech to the enemy, and they can work on reverse engineering it, while you install cutting-edge countermeasures on all mobile targets. They wasted a bunch of time and money catching up to where you were, and you're already 50 miles down the road. Then maybe you have a proxy war to show off your new tech. You keep the war cold by convincing the enemy that if they start something for real, they will not only lose, but also suffer international humiliation and disdain. It also keeps your rival in the game, so they don't give up. A cold war is good for the military-industrial complexes on both sides. Peace and consumer trade cuts in to the profit margins. Can't have people choosing butter over guns.