Balance of power, in international relations, the posture and policy of a nation or group of nations protecting itself against another nation or group of nations by matching its power against the power of the other side.

1. When countries look around them, they see that some countries are bigger and stronger. This is a clue to who might be a threat in the future.

2. There may be no obvious reason for attack. But the fact that this country is very powerful is a sign that at some point in the future it may choose to be aggressive. Governments are, therefore, very sensitive to the balance of power between their country and other countries.

States can pursue a policy of balance of power in two ways:

a. by increasing their own power, as when engaging in an armaments race or in the competitive acquisition of territory;

b. Or by adding to their own power that of other states, as when embarking upon a policy of alliances.