During World War II, Maier-Leibnitz worked at the Institute of Physics of the Kaiser Wilhelm Institute for Medical Research, in Heidelberg. After the war, he spent a year working in North America, after which he returned to the Institute of Physics. In 1952, he assumed the Chair for Technical Physics and directorship of the Laboratory for Technical Physics at the Technische Hochschule München. He became a leader in establishing and building centers which used nuclear reactors as neutron sources for research. The first was the Research Reactor Munich [ de ], which was the seed for the entire Garching research campus of the Technische Hochschule München. The second was the German-French project to construct a high-flux neutron source and found the Institut Laue–Langevin in Grenoble, France; he was also its first director. His leadership also helped establish the Physics Department at the Technische Hochschule München. Maier-Leibnitz was the chairman of a special committee for designing the German Nuclear Program, and thus he was the architect of the first full-scale nuclear program of the Federal Republic of Germany. He was a signatory of the Göttingen Manifest.