US Field artillery team

In the US system for land-based field artillery, the field artillery team is organized to direct and control indirect artillery fire on the battlefield. Since World War I, to conduct indirect artillery fire, three distinct components have evolved in this organization: the forward observer (FO), the fire direction center (FDC), and the firing unit, sometimes referred to as the gun line. On the battlefield, the field artillery team consists of some combinations of all of these elements. In other words, there may be multiple FOs calling in fire on multiple targets to multiple FDCs and any component may be in communication with some of the other elements depending on the situational requirements. Modern artillery shoots at targets miles away, a hundredfold increase in range over 18th century guns, a result of development of rifled cannons, improvements in propellants, better communications, and technical improvements such as computing the aim. The enemy is engaged at such distances that soldiers manning the guns cannot see the target that they are firing upon. Since the target is not visible, these gunners have to rely on a trained artillery observer (also called a "forward observer"), who sees the target and relays its coordinates to their fire direction center. The fire direction center uses these coordinates to calculate the specific direction, elevation for the gun, the amount of propellant (modern guns can vary the amount used) and fuse settings which the gun crew use for their gun. One component of the field artillery team is the advance party, consisting of the battery commander, his driver, first sergeant, gunnery sergeant, FDC guide, gun guides, and communications representatives. The party finds suitable positions for an artillery unit to fire from. Then they perform "route reconnaissance", which determines the suitability of the route of the unit's movement. They consider alternate routes, cover, concealment, location of obstacles, likely ambush sites, contaminated areas, route marking requirements, and the time and distance required to traverse the route.