Cold War - The Changing Relationships between the Superpowers The United States and the Soviet Union, the most important rivalry of the twentieth century, began as a partnership. This irony was caused by the fact that the Germans were conquering Europe, which forced them into this relationship. Once Hitler was eliminated and Berlin was destroyed, tensions began to rise. These two nations had completely opposite ideologies from the economic system to the political system. The changing relationship has evolved from a forced partnership, a possible world war, and now finally a stable friendship. The entire world watched as the Cold War went from moments of détente to hours on the brink of World War III. The Germans and Russians had an alliance at the beginning of the war, but Hitler turned against the Soviets. This caused the Soviets to join the British and American side and lead the advance on Germany on two fronts. The German war machine only held this alliance at bay for a time before the two nations destroyed Berlin. The Soviets already had control of everything east of Germany, and this caused great anxiety in the United States that communism was spreading. A great sense of relief came to the United States when the nuclear age began with the Manhattan Project and the bombing of Japan. Stalin now feared that the United States would one day impose capitalist ideas on Mother Russia, until the most intriguing aspect of the Cold War arose, the spies. A big change came when the Soviets began testing their own nuclear weapon in the early 1950s. . The United States could not understand how it had obtained its nuclear weapon so quickly; the answer today is so simple that the plans have been stolen. All aspects of US and Soviet life had to contend with each other. Tensions remained high during the Olympics, the space race, intercontinental ballistic missiles, the Korean and Vietnam wars. The point of maximum tension during the entire Cold War was the Cuban Missile Crisis. Up to that point the Soviet sphere of influence did not reach the Western Hemisphere except for spies. Castro had now changed this paradigm, allowing the installation of Soviet missiles in Cuba. This is the point at which most people believed we were closest to an all-out nuclear war. The real protection from this possible total war was known as MAD.