The United States Navy’s Military Sealift Command was originally formed as the Military Sea Transportation Service in 1949 to provide seaborne transportation of troops and materiel in support of overseas contingency operations, including humanitarian relief missions. As the MSTS, it played a crucial role in the supply of combat equipment, supplies, and fuel to Vietnam, accounting for 54 million tons of support materials and 8 million tons of fuel between 1965 and 1969. It was redesignated as the Military Sealift Command in 1970.
Civil mariners serve aboard MSC ships and their titles reflect normal maritime designations, but officers do wear pin-on metal insignia inspired by the Navy’s system of collar- and coat-grade insignia. However, not every Department (the equivalent of Navy Officer classifications such as Line, Chaplain, etc.) has the same number of officer “ranks” as others. The Deck Department, for instance, has four designations, ranging from Third Officer to Master, while Logistics has only two.
Two joined silver bars with the initials “MSC” between them is the insignia for several MSC officer designations:
| Department | Designation |
| Deck | Second Officer |
| Engine | 2nd Asst. Engineer |
| Communications | Ship's Comms Officer |
| Culinary | Chief Steward |
| Logistics | Jr. Supply Officer |