<P> The end of World War II saw the resurgence of previous divisions between the two nations . The expansion of Soviet influence into Eastern Europe following Germany's defeat worried the liberal democracies of the West, particularly the United States, which had established virtual economic and political primacy in Western Europe . The two nations promoted two opposing economic and political ideologies and the two nations competed for international influence along these lines . This protracted a geopolitical, ideological, and economic struggle--lasting from about 1947 to the period leading to the dissolution of the Soviet Union on December 26, 1991--is known as the Cold War . </P> <P> The Soviet Union detonated its first nuclear weapon in 1949, ending the United States' monopoly on nuclear weapons . The United States and the Soviet Union engaged in a conventional and nuclear arms race that persisted until the collapse of the Soviet Union . Andrei Gromyko was Minister of Foreign Affairs of the USSR, and is the longest - serving foreign minister in the world . </P> <P> After Germany's defeat, the United States sought to help its Western European allies economically with the Marshall Plan . The United States extended the Marshall Plan to the Soviet Union, but under such terms, the Americans knew the Soviets would never accept, namely the acceptance of free elections, not characteristic of Stalinist communism . With its growing influence on Eastern Europe, the Soviet Union sought to counter this with the Comecon in 1949, which essentially did the same thing, though was more an economic cooperation agreement instead of a clear plan to rebuild . The United States and its Western European allies sought to strengthen their bonds and spite the Soviet Union . They accomplished this most notably through the formation of NATO which was basically a military agreement . The Soviet Union countered with the Warsaw Pact, which had similar results with the Eastern Bloc . </P> <P> In December 1989, both the leaders of the United States and the Soviet Union declared the Cold War over, and in 1991, the two were partners in the Gulf War against Iraq, a longtime Soviet ally . On 31 July 1991, the START I treaty cutting the number of deployed nuclear warheads of both countries was signed by Soviet General Secretary Mikhail Gorbachev and U.S. President George Bush . However, many consider the Cold War to have truly ended in late 1991 with the dissolution of the Soviet Union . </P>

How did the relationship between the allied powers change during the cold war
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