(CNN) Here's a look at the North Atlantic Treaty Organization (NATO), headquartered in Brussels, Belgium.
The organization's charter states that the signing parties will "seek to promote stability and well-being in the North Atlantic area," and will "unite their efforts for collective defense and for the preservation of peace and security."
April 4, 1949 - NATO is established.
2014-present - The current secretary general is Jens Stoltenberg, former prime minister of Norway. On March 24, 2022, Stoltenberg's tenure was extended by one year due to Russia's invasion of Ukraine.
March 14, 2024 - The secretary general's annual report is released.
Albania (2009)
Belgium (1949)
Bulgaria (2004)
Canada (1949)
Croatia (2009)
Czech Republic (1999)
Denmark (1949)
Estonia (2004)
Finland (2023)
France (1949)
Germany (1955, as West Germany)
Greece (1952)
Hungary (1999)
Iceland (1949)
Italy (1949)
Latvia (2004)
Lithuania (2004)
Luxembourg (1949)
Montenegro (2017)
Netherlands (1949)
North Macedonia (2020)
Norway (1949)
Poland (1999)
Portugal (1949)
Romania (2004)
Slovakia (2004)
Slovenia (2004)
Spain (1982)
Sweden (2024)
Turkey (1952)
United Kingdom (1949)
United States (1949)
April 4, 1949 - The 12 nations of Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal, the United Kingdom and the United States sign the North Atlantic Treaty in Washington, DC.
July 25, 1950 - First meeting of NATO Council Deputies in London. US Ambassador Charles M. Spofford is elected permanent chairman.
December 19, 1950 - US General Dwight Eisenhower is appointed the first supreme allied commander. The position leads NATO's military operations.
March 12, 1952 - Lord Ismay is named the first secretary general of NATO and appointed vice chairman of the North Atlantic Council, which oversees NATO's political decisions.
April 16, 1952 - NATO establishes its provisional headquarters in Paris at the Palais de Chaillot.
April 28, 1952 - First meeting of the North Atlantic Council in permanent session in Paris.
May 6, 1952 - West Germany joins NATO.
May 14, 1955 - The Soviet Union and Eastern Bloc countries form the Warsaw Pact in response to West Germany joining NATO.
July 26, 1956 - Egypt nationalizes the Suez Canal. France and Great Britain use troops to intervene, against the wishes of the United States, causing a rift in NATO.
October 22-23, 1963 - NATO and the United States demonstrate the size and speed of emergency forces when flying 14,500 US troops into West Germany for maneuvers.
March 10, 1966 - France formally announces intentions to withdraw from the military structure of NATO, accusing the United States of having too much influence in the organization.
March 31, 1967 - Opening ceremony of new NATO headquarters in Casteau, near Mons, Belgium.
August 14, 1974 - Greece, angered at NATO's response to the Turkish invasion of Cyprus, withdraws from the military arm of NATO.
October 20, 1980 - Greece rejoins the NATO military structure.
May 30, 1982 - Spain joins NATO.
October 3, 1990 - Germany is reunified after 45 years. East Germany leaves the Warsaw Pact and is incorporated into NATO. In 1991, the Warsaw Pact is dissolved.
December 13, 1991 - For the first time, the Soviet Union takes part in meetings at NATO as part of the North Atlantic Cooperation Council.
December 21, 1991 - Eleven of the republics of the former Soviet Union create a new Commonwealth of Independent States. On December 25, the Soviet Union is officially disbanded with the resignation of Mikhail Gorbachev as president and supreme commander-in-chief of Soviet Forces.
February 28, 1994 - NATO forces shoot down four Bosnian Serb planes violating the UN-imposed no-fly zone. It is the first time NATO has used force.
November 21, 1995 - After the Dayton Peace Accords, the war in Bosnia Herzegovina ends. In December, NATO deploys Implementation Force (IFOR) to support the agreement.
January 13, 1996 - Russian troops are deployed to support IFOR in Bosnia.
May 22, 1997 - NATO and the Russian Federation sign a security and cooperation pact, the "Founding Act" which establishes a NATO-Russia Permanent Joint Council (PJC).
March 24, 1999 - NATO launches air strikes against Yugoslavia to end Serbian aggression in the Kosovo region.
September 12, 2001 - For the first time, NATO invokes Article V, the Washington Treaty, its mutual defense clause, in support of the United States after the September 11 terror attacks.
May 28, 2002 - NATO and Russia form the NATO-Russia Council (NRC), which makes Russia an associate member of the organization. The NRC replaces the PJC.
November 21-22, 2002 - During the Prague Summit, NATO invites seven former Eastern Bloc countries, Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia, to discuss entry into the organization.
December 4, 2002 - US Deputy Defense Secretary Paul Wolfowitz speaks before NATO in Brussels and requests that member nations contribute forces to a potential campaign in Iraq.
January 22, 2003 - France and Germany block discussion on war preparations submitted by the United States. The US proposal included provisions for Turkey's defense, the use of NATO equipment, and NATO's postwar role in Iraq.
February 10, 2003 - France, Germany and Belgium block a US request that NATO provide Patriot missiles, Airborne Warning and Control System (AWACS) aircraft, and other equipment to Turkey. The United States had made the request anticipating that Iraq will retaliate against Turkey in the event of war. Turkey invokes article IV of the NATO charter, which requires the organization as a whole to discuss security threats to any member nation.
February 16, 2003 - NATO produces three defensive plans for Turkey, in the event of a US war with Iraq:
- Deployment of NATO AWACS aircraft;
- NATO support for the deployment of theatre missile defenses for Turkey;
- NATO support for possible deployment of Allied chemical and biological defenses.
March 29, 2004 - NATO is expanded from 19 to 26 members when seven nations, Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia, and Slovenia, join in an accession ceremony in Washington, DC. All are former communist states in Eastern Europe.
August 10, 2004 - NATO AWACS begin patrolling Greek airspace prior to the Olympic and Paralympic games. NATO's presence at the Olympics is nicknamed Distinguished Games and includes AWACS and the Multinational Chemical Biological Radiological Nuclear Task Force.
September 14, 2006 - Ukraine announces that it is shelving its aspirations to join NATO, due to opposition by the Ukrainian public and Russia.
April 2-4, 2008 - NATO leaders hold a summit in Bucharest, Romania. Croatia and Albania are invited to join the alliance.
June 17, 2008 - French President Nicolas Sarkozy announces France will soon rejoin NATO's military command, 40 years after it left.
April 3-4, 2009 - The 23rd NATO summit also marks NATO's 60th anniversary. During the summit, France rejoins NATO's military command.
November 19, 2010 - NATO adopts the Strategic Concept "Active Engagement, Modern Defence" for the next 10 years.
March 24, 2011 - NATO takes command of enforcing a no-fly zone imposed on Libya by the United Nations.
March 29, 2011 - The Council of Europe rules NATO, among others, responsible for the 63 deaths of African immigrants left adrift for two weeks while attempting to reach European shores from Libya.
May 19, 2012 - Demonstrators take to the streets of Chicago prior to the start of the NATO summit. Anti-NATO protests near Mayor Rahm Emanuel's home focus on the cost of the summit to the city and city budget cuts to mental healthcare.
May 20-21, 2012 - The 25th Summit is held in Chicago. During the summit, NATO accepts US President Barack Obama's timetable to end the war in Afghanistan by 2014.
March 5, 2014 - In regard to the crisis in Ukraine, Secretary General Anders Fogh Rasmussen announces that NATO has decided to "put the entire range of NATO-Russia cooperation under review" to send "a clear message Russia's actions have consequences."
December 2, 2015 - NATO extends an official invitation to Montenegro to join the alliance.
February 11, 2016 - Secretary General Stoltenberg announces that NATO is deploying ships to the Aegean Sea to try to deter smugglers from trafficking migrants from Turkey to Greece.
June 5, 2017 - Montenegro officially becomes a member of NATO.
March 27, 2020 - North Macedonia officially joins NATO.
March 24, 2022 - NATO leaders issue a joint statement in response to Russia's invasion of Ukraine. Leaders call on President Vladimir Putin to withdraw Russian military forces, and call on Belarus to end its complicity.
May 15, 2022 - Finland's government says it intends to join NATO, ditching decades of neutrality and ignoring Russian threats of possible retaliation as the Nordic country attempts to strengthen its security following the onset of the war in Ukraine. Sweden's ruling party later said it will also support joining the alliance.
April 4, 2023 - Finland becomes the 31st member of NATO.
March 7, 2024 - Sweden officially joins NATO, becoming the 32nd member.
April 4, 2024 - Allied foreign affairs ministers meet at the headquarters in Brussels, commemorating the 75th anniversary of NATO.