How might a balance of power prevent war?

Without a balance of power one branch of government or a person might become to powerful and the country would become a dictatorship. People now and days fight against dictators this is how to prevent a war, (a civil war)

When balance of power exist between two nations, all the countries that are involved in a conflict would be fully aware that each of them had the capability to create massive destruction toward one another.

Because of this awareness, both parties would become hesitant in making initiation to start a war and might choose diplomatic method to solve their difference.