NATO then formalized the process of joining the organization with "Membership Action Plans", which aided the accession of seven Central and Eastern Europe countries shortly before the 2004 Istanbul summit: Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia, and Slovenia.

As such, opposition to Soviet-style communism became a defining characteristic of the organization and the anti-communist governments of Greece, which had just fought a civil war against a pro-communist army, and Turkey, whose newly-elected Democrat Party were staunchly pro-American, came under internal and external pressure to join the alliance, which both did in February 1952.

[11] France, however, delayed the start of the process, in part on the condition that a referendum be held in Saar on its future status, and a revised treaty was signed on 23 October 1954, allowing the North Atlantic Council to formally invite West Germany.

[12] That month the Soviet Union established its own collective defense alliance, commonly called the Warsaw Pact, in part as a response to West German membership in NATO.

[17] Franco however did sign regular defense agreements with individual members, including the 1953 Pact of Madrid with the United States, which allowed their use of air and naval bases in Spain.

[29][30] The so-called "parade of sovereignties" declared by republics in the Baltic and Caucasus regions of the Soviet Union and their War of Laws with the government in Moscow further fractured its cohesion.

Yeltsin however retracted this informal declaration the following month,[34] writing that expansion "would violate the spirit of the treaty on the final settlement" which "precludes the option of expanding the NATO zone into the East.

[45][46] In the absence of NATO enlargement, Bush administration officials worried that the European Union might fill the security vacuum in Central Europe, and thus challenge American post-Cold War influence.

Victory by the Republican Party, which advocated for aggressive expansion, in the 1994 US congressional election helped sway US policy in favor of wider full-membership enlargement, which the US ultimately pursued in the following years.

[50] Russian military actions, including the First Chechen War, were among the factors driving Central and Eastern European countries, particularly those with memories of similar Soviet offensives, to push for NATO application and ensure their long-term security.

[65] Rapid investments in their own armed forces showed a seriousness in their desire for membership, and participation in NATO-led post-9/11 operations, particularly by Estonia in Afghanistan, won the three countries key support from individuals like US Senator John McCain, French President Jacques Chirac, and German Chancellor Gerhard Schröder.

Croatian Prime Minister Ivo Sanader ultimately agreed in January 2008, as part of forming a coalition government with the HSS and HSLS parties, not to officially propose one.

[68] Albania and Croatia were invited to join NATO at the 2008 Bucharest summit that April, though Slovenia threatened to hold up Croatian membership over their border dispute in the Bay of Piran.

[71] Montenegro declared independence on 3 June 2006; the new country subsequently joined the Partnership for Peace program at the 2006 Riga summit and then applied for a Membership Action Plan on 5 November 2008,[72] which was granted in December 2009.

[129] Intensified Dialogue was first introduced in April 2005 at an informal meeting of foreign ministers in Vilnius, Lithuania, as a response to Ukrainian aspirations for NATO membership and related reforms taking place under President Viktor Yushchenko, and which followed the 2002 signing of the NATO–Ukraine Action Plan under his predecessor, Leonid Kuchma.

[130] In September 2006, Georgia became the second to be offered the Intensified Dialogue status, following a rapid change in foreign policy under President Mikhail Saakashvili[131] and what it perceived as a demonstration of military readiness during the 2006 Kodori crisis.

[186] In June 2017, Ukraine's parliament passed a law making NATO integration a foreign policy priority,[187] and President Petro Poroshenko announced he would negotiate a Membership Action Plan.

[201] On 21 November 2011, Russian President Dmitry Medvedev while addressing soldiers in Vladikavkaz near the Georgian border stated that Russia's 2008 invasion had prevented any further NATO enlargement into the former Soviet sphere.

[216] In 2009, Russian envoy Dmitry Rogozin did not rule out joining NATO at some point, but stated that Russia was currently more interested in leading a coalition as a great power.

[218] Shortly after West Germany's accession to NATO, the parties agreed to the Austrian State Treaty in May 1955, which was largely based on the Moscow Memorandum signed the previous month between Austria and the Soviet Union.

The Austrian military also participates in the United Nations peacekeeping operations and has deployments in several countries as of 2022[update], including Kosovo, Lebanon, and Bosnia and Herzegovina, where it has led the EUFOR mission there since 2009.

[219] Individual politicians from the Austrian People's Party (ÖVP) have supported NATO membership as part of European integration, including the Chancellor from 2000 to 2007, Wolfgang Schüssel and his defense minister, Werner Fasslabend.

[220] The 2022 Russian invasion of Ukraine, and subsequent NATO membership of Finland and Sweden, did lead to additional calls to re-open the issue of neutrality, including from Andreas Khol, the 2016 ÖVP presidential nominee.

[221][222][223][224] However, only the NEOS party, which then held 15 of the 183 seats in the National Council, supported a May 2022 open letter asking the government to review its commitment to neutrality,[225][226] and Chancellor Karl Nehammer, of the ÖVP, has rejected the idea.

[246] The country most recently renewed their agreement with NATO regarding interoperability in February 2024, with the issues of cybersecurity and the security of underseas communication cables in Irish waters being added as additional areas of cooperation.

[265] In February 2022, during the Russian invasion of Ukraine, Minister of Defense Armend Mehaj requested a permanent US military base in the country and an accelerated accession process to the organization, citing an "immediate need to guarantee peace, security and stability in the Western Balkans".

[6] On 3 March 2022, a resolution was passed by Kosovo's Parliament requesting that the government "take all necessary steps to join NATO, European Union, Council of Europe and other international organizations".

[287] After the overthrow of President Slobodan Milošević Serbia wanted to improve its relations with NATO, though membership in the military alliance remained highly controversial among political parties and society.

[134] On 1 October 2008, Serbian Defence Minister Dragan Šutanovac signed the Information Exchange Agreement with NATO, one of the prerequisites for fuller membership in the Partnership for Peace program.

[317] In 2014, in the run up to the self-determination referendum, the Generalitat de Catalunya published a memo suggesting an independent Catalonia would want to keep all of Spain's current foreign relationships, including NATO, though other nations, namely Belgium, have questioned whether quick membership for breakaway regions could encourage secessionist movements elsewhere.