The Allies did make use of direction-finding and other reconnaissance measures. This provided limited information, but was no substitute for the valuable Ultra messages.

Bletchley Park and BTM began work to redesign the Bombe for a fourth rotor and promised the United States that a solution would be available by August or September. The U.S. waited, somewhat impatiently, for assistance. Neither the U.S. Army nor Navy had made any breaks into the Enigma problem. Prior to entering the war, the United States was not intercepting large volumes of Enigma messages and had not seriously worked to break it. Assistance from the British would be required if the United States hoped to combat the U-boat attacks off America's coast.

Representatives of both the U.S. Army and Navy visited Bletchley Park prior to the United States' entrance into World War II and knew of Britain's success against the Enigma messages. GC&CS agreed to share information concerning the Enigma, but it was not completely forthcoming in 1941. This may have been due to security concerns. GC&CS was not confident that the United States services would be able to keep the Enigma secret. However, the adaptations to the British three-rotor Bombe were not progressing satisfactorily, and members of the U.S. cryptologic services continued to press Britain for further information.

In March 1942 the U.S. Navy contracted with the National Cash Register Company (NCR) in Dayton, Ohio, to work on the development and construction of other specialized machines. This contract established the Naval Computing Machine Laboratory (NCML). Lieutenant Commander Ralph Meader acted as the liaison between the Navy and NCR. National Cash Register's engineer, Joseph Desch, became the NCML's research director. The public knew of some of the work conducted by NCML including the production of bomb fuses, shell casings, and aircraft carburetors. However, it would be decades before the people of Dayton, or even his family, learned of the work Joseph Desch did