A military alliance is a legally binding treaty between two or more parties in which the contracting parties agree to mutually protect one another militarily in case of an armed conflict. Military alliances differ from coalitions, which are formed in response to a specific crisis and last until the crisis is resolved. Military alliances can be bilateral or multilateral. Numerous forms of military and defensive alliances have existed between states since early human history. This is a comprehensive list of former and present military alliances.

Bilateral military alliances Legend Active military alliances YearsNameMembers493 BCFoedus CassianumRoman RepublicLatin League215 BCMacedonian–Carthaginian TreatyMacedoniaCarthage433–554 Silla Baekje1123Pactum Warmundi1266–1320 Byzantine–Mongol Alliance1295–1560Auld Alliance Kingdom of France Kingdom of Scotland1373Anglo-Portuguese Treaty of 1373See also Anglo-Portuguese Alliance Kingdom of England Kingdom of Portugal1386Treaty of Windsor Kingdom of England Kingdom of Portugal1499Treaty of Blois Kingdom of France1524–1525Franco-Polish alliance Kingdom of France1528Franco-Hungarian alliance Kingdom of France1536–1798Franco-Ottoman alliance Kingdom of France Ottoman Empire1631–1639Treaty of Fontainebleau1635Treaty of Compiègne (1635) Sweden1654Anglo-Swedish Alliance England Sweden1654–1764Pereiaslav Agreement Tsardom of Russia Cossack Hetmanate1656Treaty of Marienburg Brandenburg-Prussia Sweden1672Treaty of Stockholm Sweden1716–1731Anglo-French Alliance1731–1756 Anglo-Austrian Alliance1742Convention of Turin 1756–1762Anglo-Prussian Alliance (1756) Kingdom of Prussia1756–1792Franco-Austrian Alliance1764–1788 Russo-Prussian alliance Kingdom of Prussia1773–1810Treaty of Tsarskoye Selo Denmark–Norway1778–1800 Treaty of Alliance United States1779–1783 Treaty of Aranjuez1781–1790 Austro-Russian Alliance1788–1791 Anglo-Prussian Alliance (1788) Kingdom of Prussia1790–1792 Polish–Prussian alliance Kingdom of Prussia1807 Russo-Serbian Alliance 1807–1812Treaties of Tilsit Napoleonic France1867–1868 Greek–Serbian Alliance of 18671873Treaty of Defensive Alliance (Bolivia–Peru) Peru1879–1918Dual Alliance Austria–Hungary1881–1908Austro-Serbian Alliance Austria–Hungary1892–1917Franco-Russian Alliance1902–1923Anglo-Japanese Alliance Japan1904Entente CordialeSee also Lancaster House Treaties1904Treaty of Sofia Kingdom of Serbia1913–1914Greek–Serbian Alliance of 1913 Greece Serbia1914–1918 German–Ottoman alliance1914–1918Ottoman–Bulgarian alliance1915–1918Bulgaria–Germany treaty (1915)1920–1921Polish–Ukrainian Agreement Poland Ukraine1920–1940Franco-Polish Alliance (1921) France Poland1920–1921Georgian–Polish alliance Georgia Poland1921–1939Polish–Romanian alliance Poland Romania1922–1958Anglo-Iraqi treaties of 1922, 1930 and 1948 Iraq1930–1939/40Finnish–Estonian defence cooperation1935–1939 Franco-Soviet Treaty of Mutual Assistance France Soviet Union1936–1956 Anglo-Egyptian treaty of 1936 Egypt1939–1944Anglo-Polish alliance Poland1939–1940Soviet–Estonian Mutual Assistance Treaty1939–1940Soviet–Latvian Mutual Assistance Treaty1939–1940Soviet–Lithuanian Mutual Assistance Treaty1939–1949Effectively ended in 1943Pact of Friendship and Alliance between Germany and Italy or Pact of Steel Germany Italy1940Ogdensburg Agreement1941–1945Anglo-Soviet Agreement1942–1945Twenty-Year Mutual Assistance Agreement Between theUnited Kingdom and the Union of Soviet Socialist Republicsor Anglo-Soviet Treaty of 19421946–1948Treaty of Alliance Between His Majesty in Respect of the United Kingdom and His Highness the Amir of Transjordan or Treaty of London (1946) 1947–1997Treaty of Dunkirk1950–1979Sino-Soviet Treaty of Friendship, Alliance and Mutual Assistance1951Mutual Defense Treaty between the Republic of the Philippines and the United States of America (MDT)1951U.S.–Japan Alliance1952–1977Brazil–United States Treaty1953Mutual Defense Treaty between the United States and the Republic of Korea1955–1975Simonstown Agreement South Africa1955–1980Mutual Defense Treaty between the United States and the Republic of China China (Republic of China)1957North American Aerospace Defense Command (NORAD)1957–1967Anglo-Malayan Defence Agreement (AMDA)1958Agreement between the Government of the United States of America and the Government of the United Kingdom of Great Britain and Northern Irelandfor Cooperation on the uses of Atomic Energy for Mutual Defense Purposes or 1958 UK–US Mutual Defence Agreement 1961Mutual Aid and Cooperation Friendship Treaty between The People's Republic of China and The Democratic People's Republic of Korea or Sino-North Korean Mutual Aid and Cooperation Friendship Treaty1962Thanat–Rusk Communiqué1975–1994Israel–South Africa Agreement (ISSA)1987 Major Non-NATO Ally (MNNA)Agreement applies only between the United States and Allied States1995Split Agreement2010Agreement on Strategic Partnership and Mutual SupportSee also Shusha Declaration2010Lancaster House Treaties2019Treaty on Franco-German Cooperation and Integration or Aachen Treaty2021Franco-Greek defence agreement2024Treaty on Comprehensive Strategic Partnership between the Russian Federation and the Democratic People's Republic of Korea2025Treaty between the United Kingdom of Great Britain and Northern Ireland and the Federal Republic of Germany on Friendship and Bilateral Cooperation"Conscious of the close alignment of their vital interests and convinced that there is no strategic threat to one which would not be a strategic threat to the other, the Parties affirm as close Allies their deep commitment to each other’s defence and shall assist one another, including by military means, in case of an armed attack on the other." — Final paragraph, Article 3, or Kensington Treaty2025Strategic Mutual Defence Agreement (SMDA) 2025Pukpuk Treaty2026Ocean of Peace Alliance

Multilateral military alliances Legend Active military alliances YearsNameMembersc. 7th century–338 BCLatin LeagueAbout 30 villages and tribes in the region of Latiumc. 6th century–366 BCPeloponnesian LeagueVarious city-states in the Peloponnese, dominated by Sparta478–404 BCDelian LeagueSee Members of the Delian League1167–1250Lombard LeagueNumerous cities in medieval Lombardy, modern Northern Italy1266–1320 Byzantine–Mongol Alliance1367–1385Confederation of CologneCities of the Hanseatic League1428–1521Triple AllianceThe Nahua Triple Alliance is also known as the Mexica, or Aztec Empire1508–1510League of Cambrai Aragon Kingdom of France Papal States1511–1513Catholic League (Italian) Aragon Papal States1531–1547Schmalkaldic LeagueVarious Protestant German States of the Holy Roman Empire1571–1573Holy League Papal States Spain among others1596–1604Triple Alliance (1596)1608–1621Protestant UnionVarious Protestant German States of the Holy Roman Empire1609–1635Catholic League (German)Various Catholic German States of the Holy Roman Empire1668–1672 Triple Alliance1684–1699Holy League Tsardom of Russia1689–1713League of Augsburg1699Treaty of Preobrazhenskoye Tsardom of Russia1717–1718 Triple Alliance (1717)1747–1748 Convention of Saint Petersburg1788–1791 Triple Alliance (1788) Kingdom of Prussia1815–1818 The Quadruple Alliance1815–1825Austro-Russian alliance broke off in 1853.Holy Alliance1865–1872 Treaty of the Triple Alliance Brazil1866–1868 First Balkan Alliance (1867) (1866)1873–1887 League of the Three Emperors Austria–Hungary1882–1914Triple Alliance Austria–Hungary Kingdom of Italy1907–1917Triple Entente France1912–1913Balkan League Greece Kingdom of Montenegro Kingdom of Serbia1914–1918Central Powers Austria–Hungary (1915)1916–1918 Treaty of Bucharest (1916) France Italy Romania1920–1938 Little Entente Czechoslovakia Romania Yugoslavia1934–1938 Balkan Pact Greece Romania Yugoslavia1934–1938 Rome Protocols Austria Hungary Italy1934–1935 Stresa Front France Italy1934–1940Baltic Entente Estonia Latvia Lithuania1940–1945Tripartite Pact or Axis powers1942–1945Croatian–Romanian–Slovak friendship proclamation Croatia Romania Slovakia1947Inter-American Treaty of Reciprocal Assistance (TIAR) or Rio Treaty1948–1954 Western Union (WU)See also Treaty of Brussels1949 North Atlantic Treaty Organization (NATO)1951Australia, New Zealand, United States Security Treaty (ANZUS)1953–1956Agreement of Friendship and Cooperation or Balkan Pact (1953) Greece Yugoslavia1954–1977 Southeast Asia Treaty Organization (SEATO)1954–2011 Western European Union (WEU)1955–1979 Central Treaty Organization (CENTO), formerly Middle East Treaty Organization (METO) Iran (1955–1959)1955–1991Warsaw Pact (WP)1970–1974Alcora Exercise1982Regional Security System (RSS)1984Unified Military Command (called the Peninsula Shield Force from 1984 to 2021)Military wing of Gulf Cooperation Council (GCC)1992 Collective Security Treaty Organization (CSTO)1994Compact of Free Association (COFA) 2023Alliance of Sahel States (AES)2024Trileteral alliance2025Joint Border Coordination2026Multinational Maritime Defense Alliance2026Mecca Joint Defence Agreementindirect:

Comparison of NATO and CSTO

+ Comparison of NATO and CSTO Indicators North Atlantic Treaty Organization (NATO) Collective Security Treaty Organization (CSTO) Emblem Flag Treaty The North Atlantic Treaty The Collective Security Treaty System Collective security"The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence recognised by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area." — First paragraph, Article 5, Collective security"If one of the Member States undergoes aggression (armed attack menacing to safety, stability, territorial integrity and sovereignty), it will be considered by the Member States as aggression (armed attack menacing to safety, stability, territorial integrity and sovereignty) to all the Member States of this Treaty.