The first phase of the Cold War began within two years of the end of World War II in 1945. The USSR grabbed the opportunity to consolidate control over states in the Eastern Bloc. Meanwhile, the United States was more interested in containing Soviet power, extending military and financial aid to countries in Western Europe, and creating the NATO alliance. The agreement establishing the North Atlantic Treaty Organisation (NATO) was signed in April 1949, backed by Britain, France, the United States, Canada, and other eight western European countries. Four months later, in August, the Soviet Union detonated its first atomic device, at the Semipalatinsk test site in the Kazakh Soviet Socialist Republic.