How can I build a bomb?

The threat of a Nazi atomic bomb was one of the primary driving forces behind the creation of the British Tube Alloys project which would eventually lead to the Allied nuclear weapons effort: the Manhattan Project. Several European exiles from Germany, Italy, Hungary and other nations eventually would make significant contributions to the Allied nuclear effort. The German government never did finance a full crash program to develop weapons, as they estimated it could not be completed in time for use in the war, thus the German program was much more limited in capacity and ability when compared to the eventual size and priority of the Manhattan Project.