Indirect Fire - Related Issues

Related Issues

Before a gun or launcher could be aimed it had to be oriented in a known azimuth, or at least towards the target area. There were various methods for this. Initially, the angle between the aiming point and target area was deduced or estimated and this angle set on the azimuth sight, each gun then laid on the aiming point with this angle (sometimes corrected for each gun to keep them aimed roughly parallel to each other). However, for artillery another instrument, called either a director (UK) or aiming circle (US), became widespread and eventually the primary method of orienting guns in most if not all armies. After being oriented and pointed in the required direction a gun recorded angles to one or more aiming points.

Indirect fire needs a command and control arrangement to allot guns to targets and direct their fire. The latter may involve ground or air observers or technical devices and systems. Fire may be either ‘adjusted’ or ‘predicted’. The latter (originally called ‘map shooting’) means firing data is calculated to include corrections for non-standard conditions. It also requires the target location to be precisely known relative to the gun location. Predicted fire was introduced in World War I.

Adjusting (originally ‘ranging’) means some form of observation is used to correct the fall of shot onto the target, there are several possible reasons for this:

• geospatial relationship between gun and target is not accurately known;
• good quality data for non-standard conditions is unavailable; or
• the target is moving or expected to move.

Adjusted and predicted fire are not mutually exclusive, the former may use predicted data and the later may need adjusting in some circumstances.

There are two approaches to the azimuth that orients the guns of a battery for indirect fire. Originally ‘zero’, meaning 6400 mils, 360 degrees or their equivalent was set at whatever the direction the oriented gun was pointed. Firing data was a deflection or switch from this zero. The other method was to set the sight at the actual grid bearing in which the gun was oriented, and firing data was the actual bearing to the target. The latter reduces sources of mistakes and made it easier to check that the guns were correctly laid. By the late 1950s, most armies had adopted the bearing method, the notable exception being the US.