Located at XT 640-350 in Binh Duong province, III Corps. Major VC base area and location of two VC hospitals, named C4 and C6. The forest was referred to as the "Trapezoid" by the MACV Headquarters who believed that it was the location of the VC Military Region IV Headquarters. Although the region was worked over many times by elements of III Corps, it was never made secure and remained a VC/NVA base area until 1975. The area was laced with tunnels where the VC would retreat to whenever allied forces entered the area. Thanh Dien Forest Area