From the Document: "Although the term naval forces is often used to refer specifically to Navy forces, it more properly refers to both Navy and Marine Corps forces, because both the Navy and Marine Corps are naval services. For further discussion, see 'Defense Primer: Department of the Navy.' For a discussion of the Marine Corps that focuses on its organization as a ground-combat force, see CRS [Congressional Research Service] In Focus IF10571, 'Defense Primer: Organization of U.S. Ground Forces,' by Barbara Salazar Torreon and Andrew Feickert."
CRS In Focus, IF10486
Congressional Research Service: https://crsreports.congress.gov/