Cesar Anthony Wasco was a Starfleet Marines major on the starship USS Eagle during the Dominion War. (The Star Eagle Adventures)
Wasco joined the crew of Eagle in early 2374, after the outbreak of hostilities between the Federation and the Dominion as the commander of Echo Company of the 2nd Battalion, 19th Mobile Marines Regiment which replaced the entire civilian population of the ship.
Wasco kept his Marines mostly secluded from the rest of the crew on deck 17 to continuously train, drill and prepare for combat. As a result, many crewmembers were not very familiar with Wasco or the Marines.
Their duties would include repelling boarding forces, boarding missions and special combat operations.