This is a reaction after the Chinese communist revolution and the USSR having atomic weapons.
President Harry S. Truman receives National Security Council Paper Number 68 (NSC-68). Created with input from the Defence Department, the State Department, the CIA, and other interested agencies; NSC-68 formed the basis for America’s Cold War policy for the next two decades.
NSC-68 recommended that the United States embark on rapid military expansion of conventional forces and the nuclear arsenal, including the development of the new hydrogen bomb. In addition, massive increases in military aid to U.S. allies were necessary as well as more effective use of “covert” means to achieve U.S. goals. The price of these measures was estimated to be about $50 billion; at the time the report was issued, America was spending just $13 billion on defence. It also introduced the idea of "Containment"
Truman signed in 1950 after hesitation due to the outbreak of the Korean War