The main purpose of the Manhattan Project was to develop the atomic bomb during World War II. This secret U.S. government program began in 1942, aiming to harness nuclear fission to create a powerful weapon that could end the war. Scientists, including notable figures like Robert Oppenheimer, worked in various locations, culminating in the successful test of the first atomic bomb, known as the Trinity Test, in July 1945. The project ultimately led to the bombings of Hiroshima and Nagasaki in August 1945, which played a pivotal role in Japan's surrender and the conclusion of the war.