Simplify the following text for a Grade 9 native English-speaking person.
Original: The Department of the Navy was an Executive Department and the Secretary of the Navy was a member of the President 's cabinet position , until 1949 when amendments to the National Security Act of 1947 changed the name of the National Military Establishment to the Department of Defense and made it an Executive Department . The Department of the Navy then became , along with the Department of the Army & Department of the Air Force , a Military Department within the Department of Defense : subject to the authority , direction and control of the Secretary of Defense .
Simplified: The Secretary of the Navy is in charge of the Department of the Navy , and the Department of the Navy is under the authority of the Department of Defense .