What is the designation for the rank of O-4?

The rank of O-4 is designated as Captain in the U.S. Navy and Coast Guard, and as Major in the U.S. Army, Air Force, and Marine Corps. It represents a mid-level officer rank and is critical within the hierarchy of military structure. In naval terminology, the title "Captain" holds significant responsibility, often commanding naval vessels or acting in senior staff roles.

While the options provided contain ranks that are associated with military structure, "Lieutenant Commander" actually corresponds to the O-3 rank, while "Rear Admiral (UH)" and "Vice Admiral" represent O-7 and O-9 respectively, indicating higher ranks. Understanding this structure is essential for recognizing the roles and responsibilities associated with each military rank.