WHAT IS AN FO - Forward Observer?

 An artillery observer is a soldier responsible for directing artillery fire and close air support (ground attack by aircraft) onto enemy positions. Because artillery is an indirect-fire weapon system, the guns are rarely in line-of-sight of their target, often located tens of miles away. The observer serves as the eyes of the artillery battery, calling in target locations and adjustments to the Fire Direction Center (FDC) via radio or (less commonly) landline. The FDC then translates the observer's orders into firing commands (deflection and quadrant elevation) for the battery's cannons. Artillery observers are often deployed with combat arms maneuver units, typically infantry companies or armored squadrons.
 NOTE! "Wikipedia" omission: ONLY the 105mm howitzer battalions, such as the 2/9th Arty, were tasked to provide Forward Observers. Consequently, just a "privileged few" served with the "grunts" as a full-time assignment. Many claim to be "Forward Observers" who merely went on a mission or two, but were actually assigned to base units, not exposed to combat in the field on a daily basis.
Artillery observers are considered high-priority targets by enemy forces, as they control a great amount of firepower, are within visual range of the enemy, and are often located deep within enemy territory. The artillery observer must therefore be skilled not only in fire direction, but also in stealth and, when necessary, direct combat.
Forward Observers, due to their intelligence, adaptability, and broad range of combat skills are often superb candidates for many special operations units and training. FOs are also considered to be "crazy" and "eccentric" by their peers, due to their dangerous mission profiles and their usually innate strong sense of independence, dislike for rigid authority and protocol, and general proclivity towards sarcasm, grim humor, and general disregard for rules such as those concerning uniforms, saluting, etc., which many FOs do not believe apply to them in the field. This famous streak of rebelliousness and their high esprit de corps make them a coveted, versatile and dangerous asset to many commanders' arsenals. {Apocryphal notes here, but the FOs won't dispute it}
"Let's clarify our terms...it's very important. A "real" FO is one who is assigned to be the Infantry Company commander's school-trained artillery expert...not some yahoo who overheard conversations on calling for indirect fire. That FO walks the same ground as his company grunts do, humping the jungle, and spend 24 hours out there, as long as ordered. The FO in the field can expect to participate in...and perhaps become a KIA from...a firefight, a mortar attack, a booby-trap or friendly fire...at any time. He'd better be right and better know what he is doing. It's not a "thrill-seeking" job, it is a heavy responsibility."     
                      ......{FO Dennis Dauphin, Webmaster, "The Mighty Ninth"}           
-LINK TO 2/9 Forward Observers-*