Military alliance

European military alliances prior to World War ITriple Entente and Triple Alliance
Two military alliances (NATO and Warsaw Pact) in Europe during the Cold War

A military alliance is an international agreement concerning national security, when the contracting parties agree to mutual protection and support in case of a crisis that has not been identified in advance.[1] Military alliances differ from coalitions, as coalitions are formed for a crisis that are already known.[1]

Military alliances can be classified into defense pacts, non-aggression pacts and ententes.[2]


Military alliances are related to collective security systems but can differ in nature. An early 1950s memorandum from the United States Department of State explained the difference by saying, that historically alliances "were designed to advance the respective nationalistic interests of the parties, and provided for joint military action if one of the parties in pursuit of such objectives became involved in war". While a collective security arrangement "is directed against no one; it is directed solely against aggression. It seeks not to influence any shifting 'balance of power' but to strengthen the 'balance of principle'".[3]

The obvious motivation in states engaging in military alliances is to protect themselves against threats from other countries. However states have also entered into alliances to improve ties with a particular nation or to manage conflict with a particular nation.[4]

The nature of alliances, including their formation and cohesiveness (or lack thereof), is a subject of much academic study past and present, with the leading scholars generally considered to be Glenn H. Snyder and Stephen Walt.[5]

Other Languages
العربية: حلف عسكري
asturianu: Alianza militar
български: Военен блок
čeština: Vojenský pakt
Ελληνικά: Συμμαχία
español: Alianza militar
한국어: 군사 동맹
қазақша: Әскери блок
lietuvių: Karinė sąjunga
Bahasa Melayu: Perikatan ketenteraan
日本語: 軍事同盟
oʻzbekcha/ўзбекча: Blok (bitim)
Simple English: Military alliance
српски / srpski: Војни савез
українська: Воєнний блок
中文: 军事同盟