The German nuclear energy project (German: Uranprojekt; informally known as the Uranverein; English: Uranium Society), was an attempted clandestine scientific effort led by Germany to develop and produce atomic weapons during World War II. This program started in April 1939, just months after the discovery of nuclear fission in January 1939, but ended only months later, due to the German invasion of Poland, where many notable physicists were drafted into the Wehrmacht. However, the second effort began under the administrative auspices of the Wehrmacht's Heereswaffenamt on the day World War II began (1 September 1939). The program eventually expanded into three main efforts: the Uranmaschine (nuclear reactor), uranium and heavy water production, and uranium isotope separation. Eventually i