Since the earliest weeks of the war, President Volodymyr Zelensky of Ukraine has pleaded to any government that would listen that his country was outgunned by Russia’s army. If Ukraine was going to survive, he said, it needed longer-range weapons.
Answering that call in June, Washington delivered the first batch of truck-mounted, multiple-rocket launchers known as HIMARS, which fire satellite-guided rockets with a range of around 50 miles, greater than anything Ukraine had previously possessed.
Since then, these weapons have helped Ukraine shift the momentum of the war.
On Monday, the Russian Defense Ministry said that 63 service members died on New Year’s Day in an attack on a building in Donetsk Province that officials on both sides said was carried out using a HIMARS system. Ukraine’s military estimated that hundreds had been killed in the attack.
The HIMARS system — the acronym stands for High Mobility Artillery Rocket System — is most effective when deployed against stationary targets that can be identified in advance and pinpointed, such as ammunition dumps, infrastructure or concentrations of troops. The United States has so far supplied Ukraine with at least 20 HIMARS systems, which are made by Lockheed Martin.
Ukrainian forces started to deploy the rocket launchers last summer as part of a counter offensive to recapture land in the southern region of Kherson.
Starting in late July, Ukraine used the artillery rocket system to attack the Antonivsky Bridge, cutting a key supply line for thousands of troops it had stationed in the city of Kherson on the west bank of the Dnipro River. Eventually, the Kremlin ordered its forces to withdraw from the city.
“They patiently destroyed Russian logistics and command-and-control, making it impossible for Russia to maintain forces on the west bank of the Dnipro,” said Phillips O’Brien, a professor of strategic studies at the University of St. Andrews, in Scotland, in an analysis of the war published on Substack.
Western military analysts said that Monday’s strike reflected a shift in tactics. Ukraine’s commanders had been using the rockets mostly to hit ammunition dumps and supply lines, but recently they have targeted more barracks and other troop concentrations, said Michael Kofman, director of Russian studies at C.N.A., a research institute in Arlington, Va.
“The influx of mobilized personnel at the front lines has visibly made them vulnerable to strikes,” he said.
Mr. Kofman said that the recent HIMARS strikes have had less overall impact in the war than when they were first introduced over the summer and reduced Russia’s advantage in artillery.
So far, the rocket launchers have not led to big changes to the front lines in the Donbas region in eastern Ukraine where Monday’s deadly strike on a school being used as a barracks happened. Russia has controlled much of the territory since 2014 and has significant defenses.
But the rocket launchers have been used to hit other troop concentrations in the east. Russia’s state news agency, Tass, said in December that a HIMARS had struck a hotel in Luhansk Province. Ukrainian authorities said that the hotel was a base for Russia’s paramilitary Wagner Group, which has played a significant role in Moscow’s campaign in Donbas.
Mr. O’Brien argued that weapons like the HIMARS would most likely be important as the war enters its second year.
“The first step of any Ukrainian road to victory will be the continuation of this great wasting stage we are in,” he wrote, adding that Ukraine “will rely mostly on ranged weapons to methodically dismantle the Russian forces facing them.”