of HVAP ammunition. In addition, even though it could pierce more armor than the 75 mm gun M3 mounted on the M4 Sherman tank, it did not have the high explosive firepower of the former when used for infantry support missions. Muzzle blast from 76 mm guns not equipped with muzzle brakes was also a complaint. There was also a desire for an armored roof over the turret, and it was concluded that additional armor up to one ton in weight would not impair the automotive performance of the M18. Many battalions considered the assistant driver redundant, and removed him, or stated that the vehicle should be equipped with a bow machine gun. Many crews also added additional machine guns to the turret roofs of their M18s. Pacific Theater M18s served in tank destroyer battalions and other units supporting US Army infantry divisions in the latter stages of the Pacific war, notably in the Philippines and Okinawa. Tank destroyer battalions equipped with the M18 that served in the Pacific Theater of Operations included the 637th, 670th, and 671st, although only the 637th saw combat, most notably participating in the Battle of Manila where it earned a Distinguished Unit Citation. During the Battle of Okinawa, General Andrew Bruce, who was by then the commander of the 77th Infantry Division, located eight M18s to re-equip the Antitank Company of the 306th Infantry Regiment. M18s were not issued to U.S. Marine Corps units. Korean War The M39 Armored Utility Vehicle, which was converted from the M18, was used as a prime mover, infantry carrier, and ammunition carrier. Export and legacy After World War II, many M18s were sold to other countries. Many intended for European countries under the Mutual Defense Assistance Act were rebuilt and refurbished by Brown & Root in northern Italy in the late 1940s and early 1950s, and bear data plates that indicate those rebuilds. One of the users was Yugoslavia, which received 260 Hellcats during the Informbiro period and kept some of them in reserve until the early 1990s. A number of these vehicles were later used by the Military of Serbian Krajina and Army of Republika Srpska during the Yugoslav Wars. One example was used on an armored train named the "Krajina express" (Krajina Ekspres). The Military of the Republic of China received 214 M18s, and operated them until their chassis and hulls were worn out, at which