Why might the balance of power prevent war

When two powerful countries are equally matched and both are powerful, they are less likely to go to war knowing that it lead to mass destruction and loss of life. A good example is during the Cuban Missile Crisis when the world was on the brink of nuclear war.  Fortunately both sides realized the consequences of going to war with such powerful weapons that they instead negotiated a peaceful agreement that diffused the situation.

Hdah.