The concept that world peace is best served when no one power in any region gains sufficient military strength to dominate other states in that region. The term was first used to describe European statecraft in the nineteenth century. Keeping the balance of power on the European continent was a cornerstone of British diplomacy-the concept being that if one power or coalition of powers got too strong, the weaker states would make an alliance to combat it. Alliances therefore were not a matter of ideology but of simple pragmatism; they would continually shift to maintain the balance of power. In that way an equilibrium was maintained which discouraged wars.

After World War II the idea of the balance of power was in some ways superseded by what was termed the "balance of terror," but balance of power diplomacy is always present in one form or another. For example in the 1980s, the U.S. supported Iraq in its war against Iran because it did not want Iran to become the dominant power in the region. Strengthening Iraq maintained the regional balance of power. Balance of power politics is also a factor in the U.S.'s decision to normalize relations with Vietnam. A strong Vietnam, it is believed, will act as a check on the hegemony of China in the region.