He joined the headquarters battery of the 1/10th Artillery battalion as a forward observer.  FOs direct artillery rounds to targets on the ground.  They give map coordinates of a target to the firing battery Fire Direction Center. FDCs then convert the data to settings for the howitzers.  Distance to target, fuze settings,  powder charge, direction, elevation and azimuth settings are sent to the guns.  After the first round lands, the FO adjusts the subsequent rounds to zero in on the target.  The command “Fire for effect!”  is given and all six guns deliver multiple repetitions of shells to the target.