The standoff between the United States and the Soviet Union had kept a relative level of peace for over 40 years. But the old balance of power that kept the lid on major conflicts is no longer in place, and no new system of international security has yet emerged. The balance of terror, as it was sometimes called, was indeed terrible, but it worked. Relatively small conflicts routinely broke out but they were controllable, mainly because they had to be. The major powers could not allow a small war to spread since the consequences of escalation were so great.
Today there is no such guarantee.
It was expected by many that the United Nations would assume the role of the world's watchman in the post-Cold War environment. This has obviously not been the case. The United Nations has been shown to be powerless in stopping conflict unless the combatants wanted the United Nations to be the mediator in the peace process. However, in cases where there is no willingness by the warring parties to end the conflict, such as in the Balkans, the United Nations is completely helpless. The only way to keep the combatants apart and stop the fighting in such a place is to go in with overwhelming military force and demonstrate a willingness to use it in order to keep the peace.