During the cold war, there was a point of time of tensions of nuclear war, which is the Cuban missile crisis. Khrushchev tried to transfer nuclear weapons to Cuba. This caused Kennedy to try to negotiate because they knew the consequences of the two superpowers colliding would be very dangerous. Khrushchev wasn't willing to because the US had nuclear bombs in Turkey where they were in range to attack Russia so, Khrushchev only thought having weapons in Cuba was fair. So, both nations had weapons pointing against each other so, neither had the upper hand.
I hope this helps.