The first atomic bombs were used in August of 1945. President Truman authorized their use to force Japan's surrender during World War II. The Manhattan Project developed two types of nuclear bombs, although history of the atomic bomb precedes 1945. German scientists almost developed the first nuclear weapon, but the United States achieved it first. The scientists that created the weapons used in World War II worked from an extensive foundation of knowledge acquired throughout the long history leading to the atomic bomb.
On October 11, 1939, President Franklin Delano Roosevelt sat down with an adviser to discuss a letter written by Albert Einstein. The letter informed President Roosevelt that recent developments in uranium chain reactions meant the Germans had figured out how to split uranium atoms. This put the Germans very close to the first atomic bomb. Roosevelt was hesitant at first, but he soon saw the wisdom of Einstein's words.
Einstein wrote his letter with help from Leo Szilard, a Hungarian physicist who had fled to the United States to escape the Nazis. There were many refugee scientists in the US at that time because they were fleeing Hitler's occupation. The influx of many of the world's greatest minds from several nations gave the US an advantage in developing the atom bomb. Many of those scientists considered it their duty to alert the American government that German scientists might win the atomic race. Britain eventually sent their scientists to work with with the American team as well. The British were not far from developing the atomic bomb themselves, but they did not have the resources for atomic research while they were fighting for survival against Hitler's armies.
The American effort to build an atomic bomb was given the code name the "Manhattan Project" in late 1941. Research took place at scattered universities until the Italian physicist Enrico Fermi led his team to complete the world's first controlled nuclear chain reaction. Fermi's breakthrough started a cascade of funding, and the Manhattan Project progressed at a frantic pace. Nuclear facilities were constructed in Oak Ridge, Tennessee, and Hanford, Washington. Robert Oppenheimer coordinated the entire project from the main plant in Las Alamos, New Mexico. Nearly $2 billion was spent on the Manhattan Project, and employed over 120,000 Americans.
Secrecy was essential because the Germans and Japanese could not be allowed to learn about the Manhattan Project. Technically, the Soviet Union was an ally, but President Roosevelt and Churchill agreed not to tell Stalin about the atomic bomb. The secrecy meant there was no public knowledge or discussion in the United States. The 120,000 employees were told only what they needed to know related to their division. Even Vice-President Truman did not know of the atomic bomb before he became president.
Oppenheimer supervised the first atomic bomb detonation on July 16, 1945, at the Trinity site in Alamogordo, New Mexico. A flash of intense light visible from 200 miles away was quickly followed by a 40,000 foot mushroom cloud. Windows shattered on houses over 100 miles away. President Truman was in Potsdam, Germany at the time of the test detonation, but he was quickly informed of the Manhattan Project's success.
The Allies defeated Germany in May of 1945, two months before the atomic bomb was finished. Japan refused to surrender, and President Truman was advised that a ground war in Japan would kill hundreds of thousands of US soldiers, Japanese soldiers, and Japanese civilians. Japan never responded to Truman's threat to use an atomic bomb, so he gave the order to drop the first uranium-based atomic bomb, "Little Boy," on Hiroshima. The explosion was equivalent to 12,500 tons of TNT, and it killed over 140,000 people. Japan still refused to surrender so the plutonium-based atomic bomb, "Fat Man," was dropped on August 9 over Nagasaki, killing 80,000 people. The Japanese government surrendered when the Soviet Union declared war on Japan six days later.
The United States was loosely allied with the Soviet Union during World War II, but the nations were not friendly. The US opposed Joseph Stalin's vicious policies and Communism in general. Stalin resented the US for not treating the Soviet Union as a true member of the international community. President Truman followed a policy of "patient but firm containment" to stop Soviet expansion after the war. Stalin refused to bow to US authority, and the Soviets tested an atom bomb in 1949. President Truman responded by pushing development of a stronger atomic bomb called the hydrogen bomb, or "superbomb." This started the nuclear arms race and Cold War. The hydrogen bomb vaporized the island it was tested on and had the power to destroy half of Manhattan in seconds. The US and the Soviets continued to test weapons that poured radioactive waste into the atmosphere.
The arms race also spread to space. The Soviet's launched Sputnik, the first artificial satellite, into Earth's orbit using an intercontinental ballistic missile. It sparked panic in the US government because Sputnick's launch proved the Soviet's had weapons able to hit the continental United States. President Nixon improved diplomatic relations with the Soviets, but Reagan rekindled the Cold War with anti-communist policies. The Soviet Union was experiencing such inner turmoil during Reagan's presidency that it dissolved into individual nations. The cold war ended in 1989 after the dissolution of the Soviet Union, and two years after Reagan's famous quote "Mr. Gorbachev, tear down this wall" when the Berlin wall came down.
Scientists at the University of Chicago who worked on developing the atom bomb collectively founded the Bulletin of Atomic Scientists and Doomsday Clock in 1947. The Doomsday Clock is a symbol representing the threat to humanity from reckless scientific and technical advancement. The organization came to be in 1947 because research on the atomic bomb and the devastation in Japan made it very clear that the newest weapons in the world posed a very real threat of ending the world. The Doomsday Clock was set at 7 minutes until midnight in 1947. "Midnight" signified a global catastrophe.
The Doomsday Clock reached 2 minutes until midnight in 1953 and 2018. The factors for changing the time are climate change and nuclear threat. The Doomsday Clock hasn't moved since 2018. The rationale for leaving the Doomsday Clock with 2 minutes to spare is currently based on nuclear threats. Russia is increasing aggression in Ukraine and interfering with civil wars in other nations. Russia and the US have enough nuclear weapons to destroy the world several times over. North Korea's nuclear weapons program is progressing, and peace talks with Kim Jong-un have failed repeatedly. Potentially unstable nations such as Iran and Pakistan are upgrading their nuclear arsenals. Many precarious situations across the globe could spiral into a nuclear conflict.
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