 Most of the scientists at Los Alamos were eager to return to their laboratories and universities , and by February 1946 all of the wartime division heads had left , but a talented core remained . Darol Froman became head of Robert Bacher 's G division , now renamed M Division . Eric Jette became responsible for Chemistry and Metallurgy , John H. Manley for Physics , George Placzek for Theory , Max Roy for Explosives , and Roger Wagner for Ordnance . The number of personnel at Los Alamos plummeted from its wartime peak of over 3 @,@ 000 to around 1 @,@ 000 , but many were still living in temporary wartime accommodation . To make matters worse , the water pipe to Los Alamos froze and the water had to be supplied by tanker trucks . Despite the reduced staff , Bradbury still had to provide support for Operation Crossroads , the nuclear tests in the Pacific . 
