United States Naval Computing Machine Laboratory

The United States Naval Computing Machine Laboratory (NCML) was a highly secret design and manufacturing site for code-breaking machinery located in Building 26 of the National Cash Register (NCR) company in Dayton, Ohio and operated by the United States Navy during World War II.

The laboratory was established in 1942 by the Navy and National Cash Register Company to design and manufacture a series of code-breaking machines ("bombes") targeting German Enigma machines, based on earlier work by the British at Bletchley Park (which in turn owed something to pre-war Polish cryptanalytical work).

All told, the laboratory constructed 121 bombes which were then employed for code-breaking in the US Navy's signals intelligence and cryptanalysis group OP-20-G in Washington, D.C.[4] Construction was accomplished in three shifts per day by some 600 WAVES (Women Accepted for Volunteer Emergency Service), 100 Navy officers and enlisted men, and a large civilian workforce.

According to a contemporary US Navy report (dated April 1944), the bombes were used on naval jobs until all daily keys had been run; then the machines were used for non-naval tasks.

British production and reliability problems with their own high-speed bombes had then recently led to construction of 50 additional Navy units for Army and Air Force keys.