List of military alliances

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Military alliances shortly before World War I. Germany and the Ottoman Empire allied after the outbreak of war.

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.

  NATO and   Warsaw Pact states during the Cold War era