What Is The Manhattan Project?

Learn about the Manhattan Project and its key personnel.

On October 11, 1939 a letter was delivered to President Franklin Roosevelt from European physicists Szilard and Einstein. Within this letter, the physicists warned Roosevelt about the Germans working on fission projects to create nuclear weapons. They also warned him that the development of these nuclear weapons had an excellent chance of actually occurring.

After receiving this letter, Roosevelt set up the Advisory Committee on Uranium and its first meeting was on October 21, 1939. With a lack of interest by the committee, the subject was allowed to drop until two physicists, Otto Frisch and Rudolf Peierls working in Great Britain developed a theoretical work about the fast fission of U-235. It was in this work the first estimates of the size of a critical mass bomb, its efficiency and ideas for the design of such a bomb was given. They also wrote about the ways of producing U-235. This work of Frisch and Peierls convinced the American government that nuclear fission was possible and a new committee was set up on April 10, 1940 to work on finding ways of using the Uranium. In December 1940 the committee issued a report that stated the most effective method of uranium enrichment was gaseous diffusion.

In February 1941 Philip Abelson began to develop a working uranium enrichment system (liquid thermal diffusion) and on February 26, 1941 Glenn Seaborg and Arthur Wahl discovered plutonium. In July 1941 it was found that plutonium was by far the superior fission material and the committee finished its last report in there were proposals describing atomic bombs and their construction.

Research would continue and the majority of the group of scientists that would eventually develop the atomic bomb had been brought into the "S-1 Project."

In January 1942, one of these scientists, Enrico Fermi would be transferred to a new project with the code name "Metallurgical Laboratory (Met Lab)." His work would proceed at the University of Chicago and by April of the same year, he would begin to develop the world's first nuclear reactor.

On June 18, 1942, Colonel James Marshall was ordered to take over and organize the atomic bomb's development. During August of that year he had the Army Corps of Engineers create a new "district" which as called the "Manhattan Engineer District" or what is now commonly called the "Manhattan Project."



September 17, 1942 saw a new heading for the project. Colonel Richard Groves who had just gotten through as the overseer of the Pentagon's construction was given control of the Manhattan Project. Within two days of becoming its head, Col. Groves ordered the purchase of 1250 tons of uranium ore that was stored on Staten Island and the following day purchased the 52,000 acres of land in Tennessee that would become the Oak Ridge installation. Later he would acquire the Hanford Engineer Works and 780 square miles of land in Washington State to begin construction of the plutonium reactors and separation plants. His next big step would be to ask Dr. Robert Oppenheimer to head the newly planned laboratory for the bomb's design and construction at Los Alamos, New Mexico.

With each of the three major locations of the Manhattan Project working around the clock, preparation and planning began to train flight crews in the delivery of the much-anticipated bomb. In August 1944 Groves made his first estimate as to the bomb's availability and the Air Force began modifying seventeen B-29 bombers for delivery and placed Lt. Col. Paul Tibbets in charge of organizing the 509th Composite Group at Wendover Field, Utah. The 509th would ultimately be the group to deliver the bombs in combat and Tibbets would be the pilot of the Hiroshima mission.

Things began moving quickly for the Manhattan Project in the fall of 1944 as Dr. Oppenheimer approved plans for the testing of one of the bombs in the Jornada del Muerto valley at the Alamagordo Bombing Range. This site would become the "Trinity Test Site."

The scientists were fairly certain that the uranium bombs would work but were uncertain about the plutonium bomb. Stepping up work on the research and construction the scientists began focusing on the plutonium bomb with the intention of it being the first one tested. Activity also commenced on Tinian Island to support the 509th and the assembly of the atomic bombs.

On April 12, 1945 President Roosevelt died of a brain hemorrhage in Georgia and Harry S. Truman became president. It wouldn't be until the following day that Truman was finally apprised of the fact that atomic bomb research was not only going on but also well into the building stage.

April 27, 1945 saw the first meeting of the Target Committee, which selected seventeen possible sites for the use of the bombs. They were: Tokyo Bay, Yokohama, Nagoya, Osaka, Kobe, Hiroshima, Kokura, Fukuoka, Nagasaki and Sasebo. On May 10th they would meet again and shorten the list to Kyoto, Hiroshima, Yokohama and Kokura.

During the early part of July 1945, the first bomb "Gadget" was assembled for testing at Alamagordo.

On July 14th Gadget was lifted on top of a 100-foot test tower and readied for detonation. On this same day the parts of the "Little Boy" bomb headed towards Tinian Island from San Francisco on the USS Indianapolis.

On July 16, 1945 at 5:29 a.m. the first atomic bomb (Gadget) was detonated at the Trinity Test Site with an explosive yield of 20-22 kilotons. It completely vaporized the steel tower, created a shock wave of intense heat that reached over ten miles, and the first giant mushroom cloud was seen for miles in every direction. The earthquake type of tremors the explosion caused were felt up to 160 miles from ground zero, the intense light was seen all the way into Albuquerque while windows were knocked out for a 120 mile radius.

It was also on this day that the face of war would be forever changed as the years of research and construction bore fruit in the explosion of the first weapon of mass destruction. The first use of an atomic bomb against the Japanese would occur at Hiroshima, Japan on August 6, 1945 when the B-29 Enola Gay piloted by Col. Paul Tibbets dropped its cargo of "Little Boy" upon the sleeping city below.

Following hard on the heels of this bombing, "Fat Man" was dropped upon the city of Nagasaki, Japan that in turn brought about a quick end to the war and the beginning of a new era in warfare.

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