Enlargement of NATO in the context of "Reunified Germany"

The post–Cold War era is a period of history that follows the end of the Cold War, which represents history after the dissolution of the Soviet Union in December 1991. This period saw many former Soviet republics become sovereign states, as well as the introduction of market economies in Eastern Europe. This period also marked the United States becoming the world's sole superpower.

Relative to the Cold War, the period is characterized by stabilization and disarmament. Both the United States and Russia significantly reduced their nuclear stockpiles. Much of the former Eastern Bloc became democratic and was integrated into the world economy. In the first two decades of the period, NATO underwent three enlargements, and France reintegrated into the NATO command. Russia formed the Collective Security Treaty Organization to replace the dissolved Warsaw Pact, established a strategic partnership with China and several other countries, and entered the Shanghai Cooperation Organisation and BRICS alongside China, which is a rising power. Reacting to the rise of China, the United States began a gradual rebalancing of strategic forces to the Asia–Pacific region and out of Europe.

Though tensions had existed between Georgia and Russia for years and more intensively since the Rose Revolution, an international diplomatic crisis escalated in the spring of 2008, namely after Russia announced in response to the Western recognition of the independence of Kosovo that it would no longer participate in the Commonwealth of Independent States economic sanctions imposed on Abkhazia in 1996 and established direct relations with the separatist authorities in Abkhazia and South Ossetia. The crisis was also linked to the Georgian attempts to gain a NATO Membership Action Plan at the 2008 Bucharest Summit.

Until the end of June much of the conflict between Russia and Georgia was concentrated in Abkhazia, as were both Georgian and international efforts to negotiate a peace settlement. In early July the theater had moved to South Ossetia, where skirmishes between Ossetian militias and Georgian troops turned deadly on 3 July following the attempted assassination of pro-Georgian president of South Ossetia Dmitry Sanakoyev. The conflict led to a full-scale invasion of Georgia by Russia.

The United States and Russia maintain strategic foreign relations. They have had diplomatic relations since the establishment of the latter country in 1991, a continuation of the relationship the United States has had with various Russian governments since 1803. While both nations have shared interests in nuclear safety and security, nonproliferation, counterterrorism, and space exploration, their relationship has been shown through a mixture of cooperation, competition, and hostility, with both countries considering one another foreign adversaries for much of their relationship. Since the beginning of the second Trump administration, the US has pursued normalization and the bettering of relations, largely centered around the resolution of the Russian invasion of Ukraine.

After the dissolution of the Soviet Union in 1991 and the end of the Cold War, the relationship was generally warm under Russian president Boris Yeltsin (1991–99). In the early years of Yeltsin's presidency, the United States and Russia established a cooperative relationship and worked closely together to address global issues such as arms control, counterterrorism, and the conflict in Bosnia and Herzegovina. During Yeltsin's second term, United States–Russia relations became more strained. The NATO intervention in Yugoslavia, in particular, the 1999 NATO intervention in Kosovo, was strongly opposed by Yeltsin. Although the Soviet Union had been strongly opposed by the Titovian flavour of independence, Yeltsin saw it as an infringement on Russia's latter-day sphere of influence. Yeltsin also criticized NATO's expansion into Eastern Europe, which he saw as a threat to Russia's security.