The 40th Tank Company was a tank company that served in the United States Marine Corps after it was formed in 2391. After the USN Murdock was destroyed in a battle with a Rebel flotilla in late 2390, the remains of three armored companies aboard the destroyer - the 71st, 84th and 119th - were reformed into a single new company, and redirected towards the 2nd Marine Battalion, which would soon be detailed to serve aboard the USN Starlite, an American carrier commissioned in 2388.
Acting officer of the 40th Tank, Captain Paul Vorhees, would soon lead the company among the first waves of troops to land during the Second Battle of Ganymede. They would relieve arriving troops, establish beacheads and destroy any Unity troops that would cross their path until they were ordered, along with the 90th Armored Company and five companies of infantry, to assault a crater-turned-research facility, which had since become an artillery fortress, pounding away at landing craft with stolen triple-A missiles and their own plasma weapons. After an hour, the hill was relatively secure, despite the casualties being massive.
Later, the company would take part in the First Battle of Vespene, where their heavy combat tanks would be dropped onto a butte and ordered to secure it. After the infamous nuclear detonation less than an hour later, the company would assist in gathering wounded and any survivors before making the jump back to Earth.