Became its own branch under the National Security Act of 1947
It can be safely said that the intention of the Congress was clear and 
became clearer ... and the executive branch in the future, Thus, the act was 
amended in 1949, ... organized under its own Secretary and shall function under 
the direction,... [DOC] [TLE] Truman signs the National Security Act - Jul 26, 1947 - HISTORY.com [PAR] President Harry S. Truman signs the National Security Act, which becomes one of 
... the Navy Department and War Department under a new Department of 
Defense.