The M712 Copperhead was developed at White Sands Missile Range, New Mexico and first fired in 1972. The Copperhead was developed as a high-explosive, laser-guided, anti-tank projectile that was fired from a standard M114, M777, or other 155mm howitzer and is considered to be the first “smart artillery round,” officially known as a cannon-launched guided projectile (CLGP).
Upon being fired from its howitzer, the Copperhead follows a ballistic or glide trajectory. After it reaches the apex and begins its descent phase, guidance vanes extend from the round and the onboard optical system picks up the laser-illuminated target while the guidance system maneuvers the round onto target. The target is illuminated by a forward observer using a laser target designator (LTD).
It has a large effective range, up to 16km, but several factors limit its use. It has a minimum firing range of 3km to allow the round to maneuver on target and is less effective in heavy cloud cover and in low visibility conditions. Additionally, the forward observer must keep the illumination laser trained on the target until impact, something difficult to do on a moving target or from far away.
Although the round was designed to be used against hard point targets such as tanks and fortifications, the Copperhead was used on enemy artillery, radar, and observation positions in Operation Desert Storm and Operation Iraqi Freedom in 1991 and 2003, respectively.