The modified B Reactor pile is restarted.

First Fat Man bomb assembly is completed as production gets underway. Explosive lenses and nuclear material are not yet available, the bomb assemblies are used for airdrop and ground handling practice.

First successful explosive lens tests conducted at Los Alamos, NM, establishing the feasibility of making an implosion bomb.

Work begins on an implosion initiator for the solid core bomb, it is not clear at this point if one can be made.

The first B-29 raid on Japan begins. 100 planes are launched, only 16 bombs hit the target factory.