In the the United States Marine Corps Captain is a junior officer, with the pay grade of O-3. Captain ranks above
First Lieutenant and below
Major. Captain is equivalent to a lieutenant in the other uniformed services. Its insignia is two silver bars.
Army & Marine Captains generally command company-sized units. When given such a command, they bear the title Company Commander. Captains also instruct at service schools and combat training centers and are often staff officers at the battalion level. In medical units (in all services, except Marines), captain is the entry-level rank for doctors and those possessing a Doctor of Pharmacy. In Judge Advocate General units in all services except the United States Marine Corps, captain or first lieutenant is the entry-level rank for lawyers who already have their Juris Doctor degree and have been admitted to the bar of at least one U.S. state or territory. Air Force captains' authority varies by group assignment. In the operations group, senior captains may be flight commanders while more junior captains may be heads of departments. In the maintenance and mission support groups they are almost always flight commanders. In the medical group, captains usually have little administrative responsibility as captain is the entry level rank for many medical officers. Captains in the MSC, BSC, and NC corps, however, are sometimes assigned as flight commanders.
