In the 1970s, faced with the specter of thousands of Soviet tanks possibly rushing through the Fulda Gap, the Army was looking intently for ways to rapidly kill large numbers of tanks. The TOW missile, the M1 tank, and host of other weapons were developed to face this threat.*
One development looked at the revolution in accuracy that Laser Guided Bombs had shown in the late stages of the Vietnam war, and concluded that a laser guided artillery shell would be just the thing to plink tanks. Normal artillery can make life difficult for tank formations, but the odds of actually destroying a tank are pretty slim with traditional artillery. But a laser guided 155mm artillery round, especially one with a shaped charge 6.1” diameter warhead, would destroy any tank in the world.
But there’s a big difference in the robustness required of electronics that will fly aboard an airplane, and be dropped, versus those that have to withstand the stupendous accelerations of being fired out of a gun tube.
Still, by the late 1970s, and early 1980s, American industry managed to field the M712 Copperhead laser guided 155mm Cannon Launched Guided Projectile. Copperhead required a forward observer equipped with a laser designator, and a clear line of sight to the target, not to mention reliable communications with the firing battery.
Beyond that, Copperhead actually cost a ton of money more than was originally expected. Because Copperhead was so expensive, tank killing by artillery fell instead to DPICM, or Dual Purpose, Improved Conventional Munitions. DPICM was essentially the clusterbomb of artillery. A shell was merely a carrier for a host of submunitions that would be scattered over a target area. Many of those munitions were small shaped charge warheads that could usually penetrate the thin top armor of Soviet tanks.
But Copperhead did work, and it was useful for certain very high value targets, and so it remained in the inventory, and indeed saw combat use in Desert Storm, and even as late as the invasion of Iraq in 2003.
M712 Copperhead approaches a target tank
For almost 30 years, that’s where the state of the art in precision guided artillery stagnated.
But much as the advent of the Laser Guided Bomb inspired the Copperhead, so to did the advent of the GPS/INS guided JDAM bomb inspire the next stage in precision artillery.
First up with the GPS guided G-MLRS 270mm Guided Multiple Launch Rocket System, which replace the DPICM warhead of a conventional MLRS rocket with a unitary warhead of about 250 pounds, and a guidance kit that gave it the ability to strike within just a few meters of its intended target at ranges of up to 70 kilometers.
Not surprisingly, the same technology was applied to a 155mm artillery shell, resulting the in the M982 Excalibur. The Excalibur 155mm guided projectile has been in operational use for over 7 years now. Excalibur is essentially a GPS guided missile launched from a gun tube. It both extends the range of artillery, and increases the accuracy.
But the Excalibur is fairly expensive. The entire projectile is a precision weapon. What was really wanted was a guidance kit that could be applied to existing stocks of conventional artillery ammunition to provide it was precision capability.
First up was the AMPI, Accelerated Mortar Precision Initiative, also known as the MGK, or Mortar Guidance Kit. By replacing the nose fuse of a conventional 120mm mortar round with an innovative GPS guidance system, the traditionally less than precise mortar system suddenly became capable of dropping the first round within 5-10 meters of the aim point.
It wasn’t a great leap to transform the MGK into a similar guided fuse for 155mm shells.
Unguided, conventional artillery will continue to have a place on the battlefield. But for many applications, both in the current Counter Insurgency fights, and in possible future near peer engagements, precision artillery has better effects, is a lesser logistical burden, reduced collateral damage, and can safely be used closer to friendly troops.
*By the way, the Air Force also spent a lot of time and money developing weapons and sensors for this very same role.