United States Navy rank of lieutenant (O-3) or lieutenant commander (O-4). The staffing of a Marine Corps BAS is slightly different from the Army. The battalion surgeon technically manages the BAS including the assistant battalion surgeon, either a medical officer or physician assistant medical service officer as well as corpsmen. The BAS may also be staffed by an independent duty corpsman, a corpsman trained to function independently of a medical officer and who function much in the same way as a physician assistant. A chief hospital corpsman, known as a "battalion chief", is also usually part of a BAS and supervises the other corpsmen. See also Portable surgical hospital Mobile Army Surgical Hospital Combat Support Hospital Field hospital Ambulance#Military use References Health Services Support Within the Marine Corps Operating Forces* Army Medical Department Professional Filler System Army Regulation* Military medical organizations of the United States Medical units and formations of the United States Marine Corps Medical units and formations of the United States Army