The Manhattan Project was a massive, top-secret research and development undertaking during the Second World War that led to the creation of the first nuclear weapons. Led by J. Robert Oppenheimer, the project brought together some of the world's most brilliant scientists and engineers to work in remote locations like Los Alamos, New Mexico. Their work, which was driven by the fear that Nazi Germany was also developing a nuclear weapon, culminated in the successful Trinity test and the subsequent use of atomic bombs on the Japanese cities of Hiroshima and Nagasaki, effectively ending the war in the Pacific.