Of the billions of dollars in weapons the White House has shipped to Ukraine since the Russian invasion, perhaps none have attracted as much attention as the M142 HIMARS, an advanced rocket launcher that Ukrainian troops have used to devastating effect.
HIMARS, short for High Mobility Artillery Rocket System, is a 5-ton truck that can fire long-range guided rockets. The Pentagon announced it was sending the first of four launchers to Kyiv, Ukraine’s capital, at the beginning of June, about six weeks after it started providing 155 mm howitzers and ammunition.
Since then, the United States has sent Kyiv a total of 126 such howitzers and authorized shipments of up to 807,000 rounds of ammunition for them to fire.
Ukraine now has 26 advanced mobile launchers that can fire rockets even farther than those howitzers can — 16 HIMARS vehicles from the United States and 10 older American-made M270 launchers that Britain and Germany provided.
On Thursday, Gen. Mark Milley, chair of the Joint Chiefs of Staff, said HIMARS strikes had hit more than 400 Russian targets, including command posts and ammunition depots.
The launchers are only one part of that equation. The other equally important part is the munitions they fire, called Guided Multiple Launch Rocket System, or GMLRS, rockets.
What are these things?
The GMLRS, pronounced “Gimmlers,” is an artillery rocket — an explosive weapon propelled by a solid-fuel rocket motor. It can be launched one at a time or in salvos.
The U.S. military first used artillery rockets in World War II, and they could saturate a target area with exploding warheads far more easily than a much greater number of howitzers could.
The United States largely gave up on these weapons after the Korean War. But the Pentagon began developing a new version in the 1980s as part of a suite of munitions that could destroy the tens of thousands of tanks and armored vehicles that the Pentagon assumed the Soviet Union would use in an invasion of Western Europe.
That new artillery rocket weapon, called MLRS, for Multiple Launch Rocket System, was a large tanklike weapon built on the same chassis as the Bradley Fighting Vehicle.
The M270 MLRS featured an innovative ammunition system. Its rockets were fired from bundles of preloaded launch tubes called “pods” that could be quickly discarded and replaced as a single unit, whereas older generations of launchers had to be manually reloaded one rocket at a time.
Each pod contained six unguided M26 rockets, and each rocket carried 644 small grenadelike bomblets designed to punch through the armor of an enemy tank.
The United States first used these cluster munitions in combat in 1991 during Operation Desert Storm, when more than 17,000 M26 rockets were fired at Iraqi troops, according to government records. The rocket’s bomblets had a high failure rate, leaving behind hazardous duds that could still explode if mishandled.
Dozens of American troops were killed or wounded when they encountered MLRS duds.
The Pentagon eventually decided to phase out the M26 rockets in favor of a new and more capable weapon, which became known as the GMLRS.
How is the GMLRS different from what came before?
The Pentagon initially wanted two different rockets to replace the M26 — one that contained a more reliable bomblet, and one that had a single explosive charge. They would both have longer ranges than that of the M26, as well as precision-guided accuracy.
The bomblet version, called the M30, failed to meet reliability standards and was scrapped in 2013. That left the M31 rocket, which carries 200 pounds of explosives and uses GPS signals to find its target, as the U.S. military’s main long-range rocket weapon.
The M31, which is about 13 feet long and just under 9 inches in diameter, can be fired from older M270 launchers as well as the newer M142 HIMARS, giving Ukrainian soldiers the ability to launch attacks with the explosive power of precision airstrikes.
How many has the U.S. sent to Ukraine?
Milley said Thursday that the Pentagon had given “thousands” of GMLRS rockets to Kyiv, but the exact number fired by Ukrainian forces is unclear.
Why are they having such a large impact in the war?
Ukraine had soldiers who were experienced in using artillery rockets, and they quickly mastered both the HIMARS and the GMLRS. The soldiers took advantage of the launcher’s speed — they were able to drive quickly to new targets, fire and reload fast, and drive away before Russian artillery could target their position.
The U.S. rockets had a greater range than that of the Soviet-era weapons the Ukrainian soldiers had used before, and soon they were able to attack targets Russia had believed were safely out of range, such as arms depots and command posts.
The attacks on command facilities have kept Russian leaders on the move and have disrupted their communications, making it more difficult for them to direct combat operations.
And now, Ukrainian soldiers are using the GMLRS to attack bridges behind enemy troops near the southern city of Kherson, leaving the Russians with fewer ways to escape.