Because most of his task involved construction, Marshall worked in cooperation with the head of the Corps of Engineers Construction Division, Major General Thomas M. Robbins, and his deputy, Colonel Leslie Groves.
Da de fleste af hans opgaver drejede sig om byggeri, arbejdede Marshall sammen med lederen af ingeniørkorpsets bygningsdivision, generalmajor Thomas M. Robbins og dennes næstkommanderende, oberst Leslie Groves.