The North Atlantic Treaty Organisation was founded in 1949 as a political and military alliance binding western European democracies such as Britain and France together with the USA and Canada. It was intended to defend Europe against Soviet communism, which in response built the Warsaw Pact as its own alliance bloc in Eastern and Central Europe. The basis of NATO is that an attack on any of its members will be taken as an attack upon all of them, and that the whole military might of the alliance will be mobilised in response. Because of the deep seriousness of this guarantee, new members can only join NATO if they are prepared to fully commit to collective security, and if all the existing member states vote to extend the guarantee to them.

By the collapse of communism in the late 1980s most of the western European democracies and Turkey had joined NATO, although some including Ireland, Switzerland, Sweden and Finland remain neutral to this day. The end of the Cold War brought the collapse of both the Warsaw Pact and of communism, and the future of NATO in the absence of these former threats seemed uncertain. The alliance continued, however, intervening in the Balkans in the 1990s and undertaking a peacekeeping role in Afghanistan following the 2001 campaign against the Taliban. It also continued to expand, taking in newly democratic former Warsaw Pact members such as Poland, Hungary and Romania. This expansion led NATO into friction with Moscow, which resented its former client states becoming American allies, in spite of informal Western promises to Gorbachev not to expand NATO to these states,  and hosting advanced weapons systems which it feared could be turned against Russia. Most offensive to Russia, however, was the 2004 entry into NATO of Latvia, Lithuania and Estonia, three Baltic states which had once been part of the Soviet Union itself. Despite Russian protests the Baltic countries were accepted into NATO and their forces integrated into its military structure.

NATO membership greatly appeals to the newly democratic states of Central and Eastern Europe, who remain wary of Russia and keen to associate themselves with western democracy and prosperity. In most cases, NATO membership has been followed by EU membership, although the two organisations are separate and do not fully overlap in membership. The USA has also been an enthusiast for the expansion of NATO, and has most recently championed the applications for membership of Georgia and Ukraine. These two former states of the USSR both removed pro-Russian regimes in their 2003 Rose revolution and 2004 Orange revolution respectively, events which the Kremlin saw as the result of western meddling. Since then politics in both states have been turbulent, with Ukraine split between pro-NATO and pro-Moscow elements. In most of Georgia opinion is more united, but two breakaway regions of Abkhazia and South Ossetia have resisted rule from Tbilisi and managed their own affairs under Russian patronage.

At its Bucharest conference in the spring of 2008, the United States urged its allies to offer Georgia and Ukraine Membership Action Plans (MAPs) but was unable to persuade all of its European partners to do so. Georgia and Ukraine were, however, given assurances that they would one day be welcomed into NATO; assurances which went down badly in Moscow. In August 2008 events came to a head when Georgia took military action in South Ossetia and Russia quickly sent troops into the enclave. The American-trained Georgian army was rapidly routed and Russia gained military control of both breakaway regions, and Abkhazia and South Ossetia declared their independence. Although few other states have recognised their independence, the episode has raised fears of a new Cold War and called into question the wisdom of offering Georgia and Ukraine NATO membership. This debate topic looks at what NATO should now do.