the high seas or in narrow waterways. In November 1966, the Navy PACVs were used to great effect in Operation Quai Vat (Vietnamese for "Monster", which was what the Viet Cong called the PACVs). In the operation on the Plain of Reeds, conducted jointly with Vietnamese Civilian Irregular Defense Group (CIDG) troops and Army helicopters and special forces, the PACV force brought its speed and firepower to bear on the Viet Cong, killing at least 23 of them, destroying 70 of their sampans and an equal number of their structures, taking many prisoners, and capturing their supplies. This demonstration of combat prowess in the marshy terrain in southwestern Vietnam formed the basis for stationing the Army ACVs in the Plain of Reeds along the South Vietnamese/Cambodian border. An Army evaluation found that in the Plain of Reeds, "any mission requiring ground operations can best be accomplished by ACV unts," particularly reconnaissance, light assaults, infantry transport, canal security, cordoning off areas to prevent escape, and patrolling. Though the loud noise of the PACVs was an issue, their speed made up for it in this otherwise difficult terrain, especially during the monsoon season. The PACV could clear rice paddy dikes and other solid obstacles up to high and negotiate slopes of up to . However, the PACV did not perform well in the dry season, with an Army evaluation noting that "The wetter the season, the better for vehicle operations". The Navy withdrew the PACVs for overhaul in January 1967 and redeployed them to Vietnam in early 1968. Also in 1968, the Army began employing its version of the PACV, the ACV. The Army acquired the vehicles and activated their unit, the 39th Cavalry Platoon, in January before deploying them to Vietnam in April. There were only three Navy PACVs and three Army ACVs during the whole Vietnam War. Two of the three ACVs (No. 901 and 902) were Assault Air Cushion Vehicles (AACV), weapons-heavy vessels configured for attack missions, while the other (No. 903) was a Transport Air Cushion Vehicle (TACV) configured for logistics missions. The TACV only carried the twin M60s, forgoing the .50 cal and other weapons to increase space in the cabin for carrying troops. Both AACVs were lost to Viet Cong attacks. Navy PACVs were based out of Cat Lo Naval Base and operated by Task Forces 116 and 117. The three Army ACVs were operated by