 The reactor theory developed by Fermi did not apply to the Water Boiler.Little was known about building reactors in 1943.A group was created in Bacher's P Division, the P-7 (Water Boiler) Group, under the leadership of Donald Kerst, that included Charles P. Baker, Gerhart Friedlander, Lindsay Helmholz, Marshall Holloway and Raemer Schreiber.