Forward observers in the U.S. military

Forward observers in the U.S. military are artillery observers who carry the Military Occupational Specialty designator of 13F in the United States Army and 0861 in the United States Marine Corps. They are officially called Joint Fire Support Specialists in the U.S. Army and Fire Support Marines in the U.S. Marine Corps. They are colloquially known as FiSTers, regardless of whether they are members of a FiST (Fire Support Team). The Battalion Fire Support Officer (FSO) is the Officer in Charge of a Battalion Fire Support Element.