List of military alliances

This is the list of military alliances. A military alliance is a formal agreement between two or more parties concerning national security in which the contracting parties agree to mutual protection and support in case of a crisis that has not been identified in advance. Military alliances differ from coalitions, which are formed for a crisis that already exists. Numerous forms of military and defensive alliances have existed between states since early human history. This is a comprehensive list of the most important alliances.