During the Second Taiwan Strait Crisis in 1958, the United States leased a number of artillery pieces to Taiwan to serve as a deterrent against the PRC. Among these were six M55 self-propelled howitzers, which were deployed on Kinmen Island. Purportedly, due to fears of escalation stemming from the rumoured counteroffensive by the ROCA, along with a friendly fire incident in which a ROCA unit accidentally shelled an American base on the island using the vehicle, the US requested Taiwan to return the M55s after only a week in service, in exchange for six 8-inch (203 mm) static howitzers to defend the island.

Introduced in Update "Tusk Force", the ROCA M55's main (and only) strength is its firepower: a massive 203 mm M47 howitzer, firing an incredibly powerful HE shell with approximately 23 kg TNTeq of filler. This shell is capable of destroying any tank in the game when aimed properly. However, one needs to make sure that every shot counts, as the M55 carries only 10 rounds of ammunition and the howitzer has a very long reload time. Missing a shot leaves the vehicle at the mercy of the enemy, who will be more than eager to poke holes in its large, thinly clad hull.