An international alliance is a military or political agreement between state parties that binds them to cooperate in diplomatic and economic ways for a common cause. This common cause can be national security, but it can also be a broad range of other goals. The alliance entails giving up some degree of sovereignty for a greater good, which can be a source of friction among members.
For example, in the Holy Alliance of Austria, Prussia and Russia of 1815, the states pledged “to lend each other aid on all occasions, and in every place.” This was interpreted as a promise to come to the assistance of an ally in case of war. More recently, the NATO alliance was expanded to take on a peacekeeping role in crisis situations that involve human rights violations and armed conflict.
There is a continuing debate as to whether international alliances serve useful purposes in the modern world, but their continued development to meet new security challenges looks set to continue. Alliances are a key element of the global balance of power and they reflect the concept of spheres of influence in world politics.
Moreover, they provide incentives to regional actors that may seek greater autonomy from central government authority and to align their policies more closely with those of other international alliance members. However, the extent to which this occurs varies considerably. Ultimately, it depends on the culture, social and political ties between an alliance member and other alliance members.