Rockets have been a staple of land warfare for centuries, but it wasn’t until the latter half of the twentieth century that they became a permanent addition to the U.S. Army’s arsenal. Ironically, the Army’s program to develop multiple battlefield rocket artillery to fight the Soviet Army drew inspiration for its rockets from Moscow’s wartime “Katyusha” multi-tube rocket launchers.

Battlefield rocket use dates back to thirteenth-century China. Although China is lauded for inventing gunpowder and derided for promptly using it for fireworks the reality is more complicated: China did use them for war, and even invented multiple-tube rocket launchers capable of launching up to one hundred projectiles. Rocket artillery fell out of favor for hundreds of years, but by the mid-1930s the Soviet Army had started to field the first modern rocket artillery units.

Unlike traditional gun artillery, which used a powder charge to propel a shell through a gun tube, an artillery rocket uses a continuously burning rocket motor to travel to target. The upside is that instead of a single gun tube, several tubes can be clustered together and ripple-fired mere seconds apart. As a result, rocket artillery has a faster rate of fire than tube artillery, although reloading takes longer.

The downside to rocket artillery is that rockets are less accurate. Unlike shells, whose impact point can be precisely computed by knowing the power of the powder charge, weight of the projectile and the length of the gun tube, a rocket flies free after exiting the tube, motor still burning. This makes rockets inherently less accurate and more suited to saturation attacks against area targets instead of point targets.

The Soviet Union relied on rocket artillery extensively during World War II, massing large numbers of truck-mounted multiple-rocket launchers such as the BM-13 and BM-8 to provide massed fires. Rocket artillery was extremely easy to manufacture, a critical issue when Soviet manufacturing was struggling to keep up with the war. A BM-13-16 was simply a collection of bracketed steel tubes mounted on a truck, often a Lend-Lease Studebaker, and the resulting vehicle could hurl sixteen eleven-pound high-explosive warheads a distance of 7.3 miles. What Soviet rocket units lacked in accuracy they made up with in the ability to saturate a target area, and the scream of a BM-13 launcher releasing a salvo of rockets was unearthly.

During the early 1970s, the U.S. Army refocused from Vietnam to a land war in Europe. As a result it looked to revamp its artillery capabilities with an emphasis on striking deep behind enemy lines.

The result was the M270 Multiple Launch Rocket System, or MLRS. The M270 packs twelve 227-millimeter rockets into the a box launcher and can fire all twelve rounds in less than forty seconds. The M270 is based on the chassis of the M2 Bradley infantry fighting vehicle. Tracked and highly mobile, it is designed to move into position, fire, and be ready to move to a new firing position in five minutes or less. This “shoot and scoot” tactic minimizes exposure to enemy counterbattery fire, a tactic that uses radar and other techniques to track back enemy rockets and shells in midair, determine the location of the enemy artillery units, and destroy them before they can displace to a new firing position.

Unlike other artillery units the M270 isn’t designed for direct support of ground troops. Rather, MLRS units concentrate on medium- to long-distance threats. Instead of attacking an enemy mechanized regiment on the move, MLRS units engage targets far behind enemy lines such as unit assembly areas, fuel and ammunition depots, and headquarters units. MLRS rocket fire is also ideal for friendly counterbattery fire missions.

Instead of trying to make the M270 more accurate, developer Vought decided to embrace the rocket’s lack of accuracy and maximize its ability to saturate an entire area. Each of the original M26 rockets carried 644 Dual Purpose Improved Conventional munitions (DPICM). The size of a hand grenade, DPICM rounds were ejected from the rocket while in flight, raining hundreds of the bomblets down on the enemy. The rounds were devastatingly effective against not only exposed infantry and soft-skinned targets such as fuel depots, ammunition depots and headquarters units, but were also capable of inflicting damage on tanks and armored vehicles, destroying them or putting them out of action.

The first use of the M270 was in the 1991 Persian Gulf War, when the rocket launchers earned the name “grid killers” for the ability of a single M270 to saturate a one-kilometer-by-one-kilometer box grid on a military map. A MLRS battalion has a total of twenty-seven M270s, giving U.S. Army divisions and artillery brigades incredible amounts of firepower.

An alternate munition used by the M270 is ATACMs, or the Army Tactical Missile System. A large, plump rocket, ATACMs takes the place of six rockets in an M270, meaning each vehicle can carry up to two. ATACMs was designed to attack targets even farther behind enemy lines, carrying up to 950 antitank and antipersonnel submunitions up to eighty miles. Later versions had a range of up to 186 miles.

The tendency for unexpended cluster munitions to linger on the battlefield and cause harm to civilians resulted in the 2008 Convention on Cluster Munitions. The convention bans their use and, although the United States is not a signatory, the Pentagon generally holds to the ban. As a result,  MLRS and ATACMs rockets that carried DPICM have been retired or are being updated to a single “unitary” high-explosive warhead.

The M270 was so effective that a lighter, more mobile version, the High Mobility Artillery Rocket System (HIMARS) was created. HIMARS packs six rockets or a single ATACMs on a five-ton truck. HIMARS has seen action in Afghanistan against the Taliban and Iraq against the Islamic State. The system’s usefulness against high-end threats has also seen it deployed to the Philippines opposite China, and eastern Europe opposite Russia.

The shift back to big-power warfare once again puts the focus on rocket artillery. As the U.S. Army reorients back towards fighting conventional armies again, massed fires will be back in vogue. ATACMs rockets are even getting the ability to engage moving ships at sea. New, improved rockets with GPS guidance can now destroy point targets. While rocket artillery likely won’t replace gun artillery any time soon, the versatility—and now accuracy—that rockets offer will make them critical capabilities for decades to come.

Kyle Mizokami is a defense and national-security writer based in San Francisco who has appeared in the Diplomat, Foreign Policy, War is Boring and the Daily Beast. In 2009, he cofounded the defense and security blog Japan Security Watch. You can follow him on Twitter: @KyleMizokami.

Image: MLRS combat firing practice, Republic of Korea Army. Wikimedia Commons/Republic of Korea Armed Forces