Here we see a great image of one of the six twin Mark 32 Mod 4 5″/38 caliber mounts aboard USS Alaska (CB-1), one of the only two operational battlecruisers (though termed just “large cruisers”) ever to serve in the U.S. Navy. The gun’s lookout is Corporal Osborne Cheek, and in the local control position as mount captain is Platoon Sergeant George W. Ewell. Note the local control ring sight and the binoculars and sound powered telephones worn by Ewell. If the ranks sound odd, that’s because they are not Navy GMs or strikers, but Marines.
Since the days of Tun Tavern, Marines often manned naval guns aboard the ships they were assigned. WWII battleships, carriers, and cruisers were no different. Typically each battleship had one 5-inch mount manned by Marines, as well as other mounts.
As noted by the USS North Carolina museum, the ship’s 84-86 man detachment formed the 7th Division in the Gunnery Department and were very busy.
“The Marine Detachment was in the Gunnery Department. The Marines stood lookout watch and in battle manned 20mm and (provided officers in two) 40mm mounts. (They also manned a 5-inch mount early in the ship’s career.) The Marines also furnished twenty-four hour orderly services to the captain and the executive officer. In port the Marines were responsible for the security of the ship. The Marines helped with provisioning the ship and taking on ammunition. All Marines were trained in ship to shore operations, so in addition to helping with the security of the ship in port, we were prepared to be a landing force when necessary. This was necessary near the end of the war when all Marines in our battle group transferred at sea to attack transports and went into Yokosuka, Japan. This preceded the signing of the peace treaty by several days. The Marine officers stood top gunnery watches, officer of the deck and junior officer of the deck watches, and regularly assisted in summary and general courts martials acting either as the prosecuting or defending officer.” -Captain William Romm, USMC, Marine Detachment North Carolina
When the Navy recommissioned the Iowa-class battleships in the early 1980s, the det was smaller, typically platoon-sized, but they still dedicated a 14-man gun crew to control a designated Mk28 5-inch mount, typically marked with an EGA.
As noted in the below video aboard USS Wisconsin, now a museum ship, the MARDET would rotate between manning their 5-incher, manning the ship’s 8 .50-cal M2 single mounts, and serving with the ship’s reaction force.