Also in 1949, Truman announced that the Soviet Union had successfully tested its first atomic bomb, sooner than American scientists had predicted. Even though it would have been difficult for the USSR to actually drop a nuclear bomb on U.S. soil—nuclear missiles would not be invented for another decade—the Soviets’ discovery cost Truman the diplomatic upper hand. Whereas the United States had lorded its nuclear superiority over the Soviets’ heads in the past, it could no longer do so.
To regain the upper hand, Truman poured federal dollars into the 1952 development of the hydrogen bomb, an even more devastating weapon than the original atomic bomb. Its developers feared this weapon would become a tool for genocide. The Soviet Union responded in kind with its own H-bomb the following year, ratcheting the stakes even higher. The United States and the USSR continued competing against each other with the development of greater and more destructive weapons in an arms race that lasted until the end of the Cold War.
The fall of China, the Soviets’ development of nuclear weapons, and the crises in Europe all contributed to Americans’ growing fear of Communism at home. Remembering the Bolshevik revolutionaries’ cry for the global destruction of capitalism, frightened Americans began hunting for Communist revolutionaries within the United States and elsewhere. President Truman had already created the Loyalty Review Board in 1947 to investigate all federal departments, and the State Department in particular, to uncover any hidden Soviet agents working to overthrow the government. The board went into overdrive at the end of the decade, and thousands of innocent individuals were wrongfully accused and persecuted as a result.
As a member of the House Un-American Activities Committee (HUAC), Congressman Richard M. Nixon of California helped spearhead the search for Communists in the government. In 1948, he prosecuted former federal employee and accused Communist Alger Hiss in one of the most dramatic cases of the decade. Hiss’s trial dragged on for two more years and ended with a five-year prison sentence for perjury. Prosecutors also charged husband and wife Julius and Ethel Rosenberg with having given American nuclear secrets to Soviet agents—an allegation that, though debated for decades after the trial, was corroborated by Soviet intelligence documents released in the 1990s. The Rosenbergs were convicted in 1951 and sent to the electric chair in 1953, becoming the first American civilians ever executed for espionage.
Although the Red hunts resulted in the capture of legitimate spies such as the Rosenbergs, Truman began to realize by the end of his presidency that the fear of Communism had caused widespread and undue panic. He tried to tame the Red-hunters in 1950 when he vetoed the McCarran Internal Security Bill, which he believed would give the U.S. president too much power to subvert civil liberties. Republicans in Congress, however, overrode Truman’s veto and passed the bill into law later that year.