Somervell and Styer selected Groves for the post, informing him on 17 September of this decision, and that General Marshall ordered that he be promoted to brigadier general, as it was felt that the title "general" would hold more sway with the academic scientists working on the Manhattan Project.
Somervell og Styer valgte Groves til posten og meddelte ham den 17. september denne beslutning samt, at general Marshall gav ordre til, at han skulle forfremmes til brigadegeneral, da man mente, at titlen general ville give pondus over for videnskabsmændene som deltog i Manhattanprojektet.