War Zone D

War Zone D, located in the area designated as III Corps, began approximately 10km north of Bien Hoa.

Shortly after their arrival in South Vietnam, the 173rd Airborne Brigade began their first combat operation on 27 June 1965 with an incursion with Army of Republic of Vietnam (ARVN) forces into War Zone D.[1]: 28  On 7 July troops of Company A, 1st Battalion, 503rd Infantry Regiment walked into an L-shaped ambush in the zone and killed an estimated 50 VC.

[1]: 29  From 5-8 November the 173rd Airborne and 1st Battalion, Royal Australian Regiment conducted Operation Hump in the zone.

[1]: 179 The main supply route into the zone was named the Adams Trail which began at Base Area 351 on the Cambodian side of the Phước Long Province border, tunneled its way south through a triple-canopy rainforest, skirted the eastern edge of Sông Bé Province and then passed through the western half of War Zone D. Operated by the 70th Rear Service Group, the trail terminated in northern Biên Hòa Province at a base area known to the Americans as the Catcher's Mitt (11°07′16″N 106°49′52″E / 11.121°N 106.831°E / 11.121; 106.831).

[3]: 46 From 4 December 1967 to 17 February 1968 the U.S. 199th Infantry Brigade conducted Operation Manchester to interdict PAVN/VC supply routes into the zone and keep the PAVN/VC away from Tân Uyên town and the Đồng Nai river hamlets and prevent rocket attacks on Long Binh Post and Bien Hoa Air Base.