Counterbattery
Counterbattery is a technique in artillery operations, classically defined as applying lethal force to enemy artillery that threatens, or has fired upon, one's own forces. This was relatively simple when artillery was only direct fire, so if it could hit its target, the target could see it. With the advent of indirect fire artillery toward the end of the 19th century, and as artillery range increased, the side being attacked, at first, could take no effective counteraction.
Current counterbattery is only one of the techniques used as "active defense" against enemy artillery. If facing a relatively advanced enemy who is using radar-based proximity fuzed ammunition, electronic countermeasures may be able to predetonate the rounds. The latest technique is counter-rocket, artillery and mortar (C-RAM), which actually intercepts the enemy projectiles in midair and destroys them harmlessly. C-RAM may be the only alternative when guerillas are firing from urban areas; counterbattery and C-RAM are complemetary in conventional warfare.
History
Modern counterbattery techniques were introduced in the First World War by Canadian forces at the Battle of Vimy Ridge in April 1917. Techniques developed under Andrew McNaughton were able, with only primitive electronics and no computers, were able to compute the location of German artillery in approximately three minutes. The techniques identified the sound or flash of a cannon firing, and the geographic location was calculated.
Current methods
More modern techniques still may use a sound or flash to start the tracking system and cue precision projectile-tracking radar or sensors that locate the projectile in flight. Once the projectile's trajectory is measured, computers backtrack to the point of origin. In the 1970s, the target acquisition team had to pass the position to the gunners, who would manually compute a fire pattern.
Current techniques automate aiming the howitzers or multiple rocket launchers at the enemy weapon, fast enough that counterbattery fire is often in the air before the enemy projectile lands. If counterbattery is fast enough and lethal enough, a hostile artillery unit will not get a second chance to fire. As a consequence, "shoot and scoot" techniques are used against forces that have modern counterbattery capabilities: artillery pieces such as the U.S. M109A6 self-propelled howitzer or the M270 Multiple Launch Rocket System multiple rocket launchers are mobile, and, seconds after firing, are moving to their next position.
Since artillery batteries are often spread-out targets, counterbattery will, at a minimum, involve multiple blast-fragmentation shells fuzed for airburst over the target area. A typical U.S. response, especially when the enemy artillery is in an area where there may be civilians, is six M107 high-explosive shells from 155mm howitzers.
When the enemy weapon is in open areas, as with desert warfare during Operation DESERT SHIELD, the counterbattery munition of choice has been cluster submunitions, that spread out more efficiently than airbursts. A significant number of antipersonnel or "dual-purpose improved comventional munition" bomblets do not detonate on impact, but remain hazardous if disturbed. Effectively, such munitions create an antipersonnel minefield, and there are strong international initiatives to ban antipersonnel mines.