Updated 1 May 2014

This set of pages describes British artillery technical fire control during the 20th Century, this lies at the heart of indirect fire.  The pages are in two groups.  One group of six pages describes the methods in six different  periods between about 1900 and 2000.  It's worth starting at the beginning, Before World War 1, and following the whole story through to the Computer Age.  The other group of five pages deals with five different technical subjects that underpin technical fire control , these cover their special subjects over the World War 2 period.  

The essence of indirect fire, which means that guns can attack any target in range not merely in view from the gun position, is that the gunners have to be told where to aim. It means there must be some way to relate the guns to the target, this has three elements:

• People elsewhere have to 'acquire' the targets and direct the guns' attack on them.
• There must be some geo-spatial framework to relate the guns to their targets.
• Firing data has to be produced, applied to the guns' sights and the guns layed.

These pages are about what happened at the gun position for the second and third. This is sometimes called `technical fire control' to differentiate it from the target acquisition and fire direction activities or `tactical fire control'.  The British approach to technical fire control was significantly different to that of some other armies.  The British never tried to do it above battery level.  Furthermore until about 1950 some technical fire control could optionally be done by a person who could see the target.

The overall problem has two elements, methods for producing the firing (ie aiming) data, then methods for aiming the guns using the firing data.  Aiming has two or three components:

• aiming in the horizontal plane, variously called 'line', 'direction' or 'azimuth';
• aiming in the vertical place, usually called 'elevation'; it deals with the distance from guns to target and any difference in the altitude of the two locations, usually called the 'range' and converting this to an elevation angle; and
• setting the fuze if the shell is to burst in the air and not at impact with the ground, unless the fuze can 'sense' the proximity of the ground this is done by determining the fuze 'length', the length of time between firing and the 'fuze event'.

The first problem was solved fairly quickly, a Russian officer had worked it about in about 1880.  Nevertheless  it took a while for the necessary sighting instruments and  methods of using them to appear.  This is described in more detail in Laying & Orienting the Guns.  If there was an observer to watch the fall of shot and report his observations or order corrections then the gunnery processes for producing firing data were fairly straightforward.

However, World War 1 (WW1) quickly introduced the need for 'map shooting', where the target was in the enemy's depth (or at night) and could not been seen and ranged by an observer.  By late 1917, notably the battle of Cambrai, the benefits of map shooting as a means of achieving surprise were fully recognised although its use had started two years earlier for counter-battery fire by heavy artillery.  Map shooting meant that corrections for non-standard conditions had to be calculated.

20^th Century artillery practice generally related the battery to its target by finding the map (or rectangular) co-ordinates for both and then producing polar co-ordinates (azimuth and distance) between them.  This azimuth and distance may then be corrected for non-standard and local conditions such as meteorological, gun wear and ammunition variations. The processes are outlined on the Ballistics, Meteor, and Calibration pages.  Using rectangular co-ordinates means having survey data for guns and target and or maps, preferably gridded, on which guns and target could be accurately plotted.  However, in WW1 British artillery did not use rectangular coordinates that enabled calcualtion of polar coordinates, instead they used squared map sheets.  Survey is explained on the Maps & Survey page. 

Correcting for local conditions can be done in one of two ways, or use them both:

• An observer watches where the shells fall and corrects them onto the target.
• Someone calculates the effects of the local conditions and applies them to the bearing, and distance before opening fire.

In British terminology the former was called `ranging' and later `adjusting'. The latter was called `map shooting' and later `predicted fire'. Of course if map shooting was inaccurate then ranging was still required to hit the target.

All this highlights that there are several related issues in indirect fire:

• Having some means of aiming the guns at a target they cannot see. This means having a frame of reference to connect the guns and their targets and well as the right sort of sights and the means of producing data for those sights. It is the foundation of indirect fire.
• Being able to measure the actual muzzle velocity of guns and use this data to ensure that their shells land together and closer to the target than would otherwise be the case.
• Being able to measure and make allowance for the meteorological conditions of the moment. This is essential if ranging is either impossible or forbidden, particular when conditions are significantly different to standard and or when firing at more than a very few thousands of yards.

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