Which military branch was NOT established as a result of the National Security Act of 1947?

The correct answer highlights that the Marine Corps was not established as a result of the National Security Act of 1947. This act, which was a significant restructuring of the U.S. military following World War II, led to the creation of the Department of Defense and the United States Air Force as a separate branch.

The Marine Corps, however, has a much older history, having been established in 1775, well before the enactment of the National Security Act. The act was primarily aimed at reorganizing the existing military structure and roles to better respond to the needs of the post-war era.

In contrast, the Navy was also established long before 1947, as it dates back to 1775. The National Security Act did not create these branches; it rather reorganized the military and established new command structures, particularly emphasizing joint operations and coordination between the various branches.