By 1939, it was apparent that the government of Germany was rearmed and preparing to reclaim territories on the eastern and western borders that had been lost in World War I. An alliance with Italy and Japan caused concern in Europe and the United States, as another large-scale conflict seemed inevitable.

To compound these concerns, power-producing fission had been dis­covered in Germany, the country that was now making aggressive moves. It was a logical conclusion that the Germans would be pursuing the devel­opment of nuclear weapons, as they were scientifically able to do with a strong motive and a well-developed industrial economy. The use of nuclear armaments, with their extreme power concentrated into small singular weapons, would obviously shorten a major conflict and reduce its cost. These considerations were not lost on the major governments in Europe, and defensive measures were implemented quickly as a result. England rushed its Home Chain radar early-warning system into opera­tion, and France shored up its Maginot Line buried defense system on the northern frontier.

The Germans did start several nuclear weapons programs in secret as war clouds were forming, but no such weapon was used in the European theater of World War II. As the smoke dissipated in 1945 after the German surrender, it became clear that there had been nothing to worry about after all. The Germans had not even achieved a self-sustaining nuclear chain reaction, much less a nuclear explosive. The reasons for this failure are interesting.

The German atomic bomb program began early, just months after the discovery of fission in uranium. It was given the name Uranverein, or the “Uranium Club.” There were misgivings, even at this earliest starting point. Carl Friedrich von Weizsacker (1912-2007), one of the German par­ticipants in the effort, remembers the feeling:

To a person finding himself at the beginning of an era, its simple funda­mental structures may become visible like a distant landscape in the flash of a single stroke of lightning. But the path toward them in the dark is long and confusing.

Weizsacker and others worried that wars waged with atomic bombs could not be won, as both sides would be wiped out. “But the atom bomb exists,” he said. “It exists in the minds of some men.”

The first task facing the Uranium Club was to produce a self-sustaining nuclear reaction, and for that purpose a neutron moderator, or a material to slow neutrons to fission speed, would be needed. An obvious material was graphite, because carbon would not capture neutrons and remove them from the fission process. A low neutron capture probability was critical at this beginning point, because of the very small component of usable U-235 in mined uranium. The sustained nuclear fission in a chain reaction experiment using natural uranium would barely work, and it would be sensitive to neutron loss. The loss of a tiny percentage of fission neutrons to nonproductive absorption would shut the reactor down. This meant that graphite was unusable, because European industrial graphite contained trace amounts of neutron-absorbing impurities, such as boron. For the same reason, pure distilled water would be unusable. The hydro­gen in water has a slight tendency to capture neutrons. A solution was to use heavy water, or deuterium-oxide. Deuterium is a hydrogen atom with a neutron precaptured, and it is unlikely to capture another. It was decided to build the German nuclear reactor using heavy water as a mod­erator. This decision would slow down the development of the German reactor considerably, as heavy water rarely occurs in nature, and it must be separated from natural water at great expense and effort.

The second reason for the loss of speed in the German atomic bomb development was that the entire Uranium Club was called to military service four months after it formed. The club was reformed on Septem­ber 1, 1939, the day World War II officially started, and, under the direc­tion of the Army Ordnance Office, research into the feasibility of nuclear weapons was conducted with moderate funding. The third reason for the loss of speed occurred on February 26, 1942, when a critical meeting was held by the Research Council to report on the technical progress and make recommendations for further work. All the top people in the Ger­man government and military were invited, but unfortunately included with the invitation was a copy of the lunch menu. Trying to impress the

government officials with the depth of their research expertise, the sci­entists had planned an experimental lunch. The food was to consist of several types of vitamin-enriched morsels, all fried in “synthetic lard.” All the invited officials found something else they had to do that day, and the German atomic bomb program sustained a crippling delay.

Perhaps the most important reason for the slowdown in the German nuclear development program was the emigration of some of the finest theoretical and experimental physicists in the world. Newly implemented laws under the Nazi and Fascist governments of Germany and Italy cleared the universities of all research and academic faculty of Jewish heritage and even visiting Jewish professors from Hungary were forced to leave. They spread west, first to Great Britain and then to the United States.