At the end of WWI, the defeated Germans and their allies were forced to sign the Treaty of Versailles. This treaty, which imposed harsh reparatory fees on the defeated nations and crippled their economies, but also gave rise to the League of Nations, was never signed by the United States. When Hitler took power in Germany, he repeatedly violated the treaty, but since the countries of Europe were so devastated from World War I, the League chose to practice appeasement instead of stopping the tyrannical ruler in power. Eventually, after a period of appeasement, the aspirations of the German and Japanese rulers became too great, and WWII started. The United States, which tried to remain neutral, got dragged into the war due to a number of reasons, one of which was the bombing at Pearl Harbor by the Japanese. The United States quickly went to work on a new weapon of mass destruction in the Manhattan Project.

By the time an atomic bomb had been successfully detonated in Alamogordo, the war in Europe was coming to a close. The only opposition left was the Japanese Army and the ideological conflicts with the Soviet Union. When the U.S. dropped atomic bombs on Hiroshima and Nagasaki in 1945, numerous reasons, such as saving American lives and ending the war quickly were involved in the decision. One widely accepted reason for dropping the atomic bomb was to save the thousands, or millions, of American lives that would be lost in the coming invasion of Japan. It was seen that while trying to take over Iwo Jima, a small, five-square-mile, area, that 26,000 marines were killed in battle.

This led the American Army to believe that the Japanese would fight until the last man. Because of this ideology, Americans believed that a full-scale invasion would cost at least a million lives (Document A). President Truman officially decided to use the bomb because he thought it would save thousands of lives, and his idea was supported by many military advisors and scientists (Documents G and H). Although the bombs killed almost 100,000 Japanese, many of them civilians, it saved at least ten times as many American lives and stopped the necessity for five-million Japanese soldiers to go into battle.

Another reason America wanted to drop the atomic bomb was to end the war quickly, and not to have the allied armies get involved. Should Truman have decided not to drop the bomb, it would have taken at least another six months to defeat the already collapsing Japan (Document B and F). Also, agreements with the Soviet government earlier would require that the Red Army get involved in the war as well (Document D). Soviet involvement on the Japanese front could have lead to negotiating problems after the war was over, and so the U.S. wanted to end the war quickly to avoid post-war negotiations (Document C).

Pressure from men such as Eisenhower and Winston Churchill to end the war quickly eventually led the United States sending out an ultimatum to Japan. When Japan didn't surrender, America had no choice but to drop the atomic bomb on Japan. Although it is widely accepted that Truman dropped the bomb to save time and save lives, speculation about the Cold War that ensued led some historians to believe that the U.S. dropped the bomb to display its military capabilities to the Soviet Union. Alpurez argues that the United States was afraid that the Soviet Union were trying to incite revolution in the countries of Europe and dropped the atomic bomb as an ultimatum to Stalin. Anti-Soviet feelings had already began to arise due to the ideological differences between the two superpowers.

The new Secretary of State, James Byrnes, felt that Russian influence would spread in Europe and that dropping the bombs would keep them in check (Document F). Harry Truman, the president at the time, also saw Communism as a threat to democracy and the free world. Because of the heightened feelings of distrust for the Russians, many historians have previously thought that the decision to drop the bomb was a tactical measure to scare the Soviet Union. After the dropping of the bombs on Hiroshima and Nagasaki, the war with Japan promptly ended in unconditional surrender.

However, after the war, the United States and Russia were the only two superpowers. Diplomatic relations between the two countries slowly degenerated into a Cold War. Both countries were in competition to have the larger army and to have more of the world behind them. The ideological differences between the two powers had manifested itself in a competition that imperiled the entire globe.

The conflict between Communism and Capitalism became very real, and the only thing that kept the two powers from destroying each other was the idea of Mutually Assured Destruction. This conflict of ideas began brewing back in the time of WWII and the conquest of Japan.