Throughout the Cold War, the North Atlantic Treaty Organization (NATO), also known as the North Atlantic Alliance, stood as a critical defense against a Soviet invasion of Europe. The core principle of NATO was that an armed attack against one member in Europe or North America would be considered an attack against all, a vital assurance for European nations facing the threat of massive Soviet and Warsaw Pact forces. Lord Ismay, NATO's first Secretary General, pragmatically summarized its purpose as keeping the Russians out of Europe, the Americans in, and the Germans down. For four decades, Europe relied on the U.S. through NATO to deter the Soviet Union, providing a security guarantee that allowed European nations to allocate fewer resources to defense. However, since the dissolution of the Warsaw Pact and the collapse of the U.S.S.R. in 1991, the 28-member Alliance has struggled to define its purpose. Without a clear threat, NATO enlargement became a goal in itself, and interventions in the Balkans and Afghanistan failed to unify the alliance. Member states have developed divergent threat priorities, with the U.S. focusing on militant Islam abroad while most European nations treat terrorism as a domestic issue. Russia's resurgence has caused concern among Eastern European NATO members, but Western and Southern Europe, particularly Germany, show little alarm and instead favor cooperation with Russia. European NATO allies are increasingly divided on the primary reason for the alliance's continuation. France and Germany, entertaining a Russian proposal for a new European Security Treaty, indicate a shift away from viewing NATO as essential to their interests. They no longer see Russia as a threat and seek to avoid involvement in costly American military endeavors. Although NATO remains technically viable, it is becoming apparent to many members that it may have outlived its usefulness, signaling the potential beginning of its end.

Russia's aggressive maneuvers have heightened tensions with NATO, particularly in the Baltic region. Putin has threatened cyberattacks if NATO continues to build up its rapid-reaction force in the Baltic States, and he has hinted at a range of offensive options, including nuclear escalation to World War III, if NATO attempts to reverse his annexation of Crimea. Russian officials have warned that Moscow would respond forcefully, potentially with nuclear force, should Western nations try to wrest control of Crimea from Russia. Additionally, Putin's deputy cautioned that the Russian people would demand a strong response if NATO sent arms to Ukraine, noting similar conditions in Lithuania, Latvia, and Estonia, where significant ethnic Russian populations reside. Putin aims to draw these ethnic Russians toward Russia without provoking NATO to deploy troops, a move that could position NATO as a co-aggressor against Russian-speaking minorities in the Baltic States, creating a situation potentially more dangerous than the conflict in Ukraine. NATO has faced increased Russian military activity, with warplanes scrambling 400 times in 2014 to counter incursions not seen since the Cold War. In March 2015, NATO's Baltic Air Police Mission spotted and intercepted eleven Russian military aircraft near Lithuania. More recently, Swedish forces identified and pursued Russian bombers and fighters near Gotland and Bornholm, while NATO jets intercepted four Russian planes over the Baltic Sea heading toward Kaliningrad. On the naval front, Sweden deployed minesweepers last October to search for a suspected Russian submarine near Stockholm. Russian ambassador Mikhail Vanin also warned Denmark that its warships could be targeted by nuclear missiles if it joined NATO's missile defense system. In response to Russia's military buildup in the Arctic, including arming the Northern Fleet with new nuclear submarines and reviving Soviet-era bases, neighboring countries are adjusting their defenses. Norway plans to increase military spending by 3.3% despite economic challenges and is restructuring its forces to address these threats. Finland, historically nonaligned, is now considering NATO membership, a once-unthinkable idea gaining public support. As Russia's Cold War behavior resurfaces, European nations are shifting to a more vigilant stance in the face of these escalating tensions.

On May 12, 2011, the Visegrád Group announced that its four nations—Poland, the Czech Republic, Slovakia, and Hungary—are forming a battle group, ready by the first half of 2016 and commanded by Poland. This force will be independent, not under NATO's authority. However, starting in 2013, these countries will participate in regular military exercises with the support of the NATO Response Force. The Visegrád Group obviously questions NATO's ability to defend it from Russian or any other power's aggression. The new NATO strategic concept, publicized in the last quarter of 2010, indicates that the United States, stretched thin by ongoing wars, is reducing its commitment to European security. Under this plan, should Poland come under attack across the North European Plain, the U.S. would send only one brigade to defend it.