Compton asked theoretical physicist J. Robert Oppenheimer of the University of California, Berkeley, to take over research into fast neutron calculations—the key to calculations of critical mass and weapon detonation—from Gregory Breit, who had quit on 18 May 1942 because of concerns over lax operational security.
Compton bad den teoretiske fysiker J. Robert Oppenheimer fra Berkeley om at overtage ansvaret for forskningen i hurtige neutronkalkulationer — nøglen til beregning af den kritiske masse og detonering af våbenet — efter Gregory Breit, som havde taget sin afsked den 18. maj 1942 på grund bekymringer over slap operationssikkerhed.