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.
Source: Wikipedia — Forward observers in the U.S. military (CC BY-SA 4.0)