 The main US Army operation took place in an area about north of Bien Hoa, where the US 1st Battalion, 503rd Infantry Regiment (1/503), 173rd Airborne Brigade conducted a helicopter assault on an LZ northwest of the Dong Nai River and Song Be River.The 1st Battalion, Royal Australian Regiment (1RAR) was deployed south of the Dong Nai.In a part of the operation (known later as the Battle of Gang Toi), 1RAR attacked a VC bunker and trench system.