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Why U.S. HIMARS Rockets Are Becoming Increasingly Decisive for Ukraine

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Updated: | Originally published:

On New Year’s Day, Ukraine used American-made rockets to kill dozens—and possibly hundreds—of Russian soldiers within its borders. (Russian officials said the strike resulted in the deaths of 89 service members, while Ukrainian officials suggest the casualties are in the hundreds.) It marks one of Ukraine’s deadliest attacks on Russian forces in the war.

Officials from both countries say that HIMARS rockets, which are satellite-guided weapons with a range of about 50 miles, were used in the attack.

The U.S. first provided Ukraine with long-range HIMARS rockets back in June; they offered roughly twice the range of the weaponry that Kyiv were previously using.

Here’s what to know about HIMARS rockets, and why they have become essential for Ukraine’s war operations.

What are HIMARS rockets?

HIMARS, produced by Lockheed Martin, stands for High Mobility Artillery Rocket System.

“HIMARS is one of the world’s most advanced rocket artillery systems; its range is farther than anything the Ukrainians had, so when that was transferred they did get the ability to strike targets deeper behind the front-lines and much more accurately,” says Ian Williams, deputy director of CSIS’s Missile Defense Project.

They are considered most effective for attacking stationary targets such as infrastructure and troops in a concentrated area.

HIMARS rockets have been integral for Ukraine in a defensive and offensive capacity in the war against Russia, experts say. “HIMARS have liberated strategically significant Ukrainian cities and territory that likely otherwise wouldn’t have happened… It’s a glowing report card,” says George Barros, an analyst on the Russia and Ukraine portfolio at the Institute for the Study of War.

How has Ukraine used HIMARS rockets against Russia?

HIMARS rockets have been particularly effective in fighting Russia’s offensive in Donbas by allowing Ukraine to attack Russian supply and ammunition depots.

They were also crucial in forcing Russia to withdraw from Kherson. “That was only possible because the Ukrainians had this extended strike capability to degrade those bridges. Without the HIMARS, I don’t think the Ukrainians would have liberated Kherson,” Barros says.

Until the New Year’s Day attack, HIMARS rockets had mostly been used to target Russian infrastructure. “What’s different about the recent strike is that they hit an area where there happened to be a lot of Russian military personnel, so there was a very high casualty count,” Williams says. “What we’ve seen until now is HIMARS being used to target Russian logistics and weapon and artillery stockpiles.”

The U.S. role in supplying HIMARS to Ukraine

The U.S. has supplied at least 20 HIMARS launchers to Ukraine. Their announcement to provide the weapons in June was part of a larger $700 million military aid package.

U.S. officials say that there are certain restrictions placed on the HIMARS rockets provided to Ukraine. They can’t fire ATACMS missiles, which have a range of almost 200 miles. The U.S. also sought Ukrainian assurances that HIMARS would not be fired into Russian territory.

Analysts say these kinds of restrictions are the U.S.’ way of preventing their support for Ukraine from growing into a larger conflict between the U.S. and Russia.

Some call for the U.S. to continue to limit the kinds of weapons provided to Ukraine. “The United States should avoid encouraging or facilitating a Ukrainian effort to fully expel Russian forces from all of its territory, including Crimea, a war aim that would run too high a risk of prompting [Russian President Vladimir] Putin to undertake even more reckless actions, including the possible use of nuclear weapons,” said Charles Kupchan, the top National Security Council official for Europe during the Obama administration, according to the Wall Street Journal.

But Williams says the idea that U.S. weapons used to strike targets inside of Russia, as opposed to homegrown systems, could be seen as more escalatory is flawed. “I don’t think that’s the case personally but that seems to be a line that the [Biden] administration has drawn,” he says.

As the war continues, Ukraine’s access to effective weaponry will be key in shaping their response to Russian aggression. Even with the HIMARS, they are requesting Western allies to also provide them with tanks; the U.S. has refused.

Barros worries that restrictions on weapons may hamstring Ukraine’s efforts to fight back effectively. “We’re not going to get into World War III with Russia by sending Ukrainian weapons [and]… sending them longer range artillery,” he says.

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Write to Sanya Mansoor at sanya.mansoor@time.com