with either a 40mm Mk 19 grenade launcher or .50 caliber M2 Browning machine gun. The FAV was designed to provide highly mobile firepower that could attack the flanks of heavier mechanized units. Some variants also mounted TOW missiles. All of these weapons systems were attached to the FAV by a mount designed to break away if the vehicle rolled over, which they were prone to do. The FAVs were problematic at best and were eventually replaced by various versions of the Humvee/HMMWV light truck. The combined arms battalions were organized as a mix of assault gun companies and light motorized infantry companies, with the heavy battalions fielding two assault gun companies and one light motorized infantry company, while the ratio was reversed in the light battalions. The assault gun companies were to be equipped with the Armored Gun System (AGS), but because of delays in the AGS program they were initially equipped with M901 ITVs Improved Tow Vehicles, then M551 Sheridan light tanks and later with Humvees with TOW missiles or Mk 19 grenade launchers. Light motorized infantry companies were equipped with Humvees mounting a Mk 19 grenade launcher. Each combined arms battalion also fielded a combat support company equipped with mortars, scouts, and an anti-armor platoon slated to be equipped with Humvees mounting a ground version of the Hellfire missile. As this Hellfire version never entered service, the platoons were later also equipped with Humvees with TOW missiles. The division's first and third brigade were to field one of each of the three new battalions, while the second brigade would field three combined arms battalions heavy. The third brigade was to field one light and one heavy combined arms battalion and the 9th Cavalry Brigade two attack helicopter battalions, one combat support aviation battalion, and one cavalry reconnaissance squadron. The division artillery would consist of three battalions equipped with M198 155mm towed howitzers, one light artillery rocket battalion with M102 105mm towed howitzers and M270 Multiple Launch Rocket Systems, and one target acquisition battery. The division support command would field three forward support, one cavalry support and one main support battalion. However, because of the delay of the Armored Gun System the division did only activate four of the envisioned five combined arms battalions heavy and retained the 2nd Battalion, 77th Armor instead. Parts of the division were organized at the end of the 1980s as follows: 9th