Joe Biden has announced the US will send advanced missile systems to Ukraine. The new weapon is the Himars multiple launch rocket system, or MLRS: a mobile unit that can simultaneously launch multiple precision-guided missiles.
Both Ukraine and Russia already operate MLRS, but Himars has superior range and precision.
What system will the US provide?
The M142 Himars system (High Mobility Artillery Rocket System) is a modernised, lighter and more agile wheel-mounted version of the track-mounted M270 MLRS developed in the 1970s for US and allied forces.
The Himars that Washington is providing to Ukraine will have a range of about 50 miles (80km), a US official told reporters.
Himars units carry one preloaded pod of six 227mm guided missiles (the M270 carries two pods), or one large pod loaded with an Army Tactical Missile System (ATACMS) tactical missile. The US will not supply Ukraine with the ATACMS, which has a range of 300km.
With a small crew, the Himars can remove a spent pod and load a fresh one in minutes, without other vehicles helping. The crews will require some training.
The US military already has Himars units in Europe; and Nato allies Poland and Romania have acquired the systems.
Why are they valuable?
Himars will give Ukraine’s forces the ability to strike further behind Russian lines, and at distances better protected from Russia’s own long-range weaponry.
The GPS-guided missiles the Himars shoots have a range about double that of the M777 howitzers that the US recently supplied to Ukraine forces.
At roughly 80km it generally puts Himars out of range of Russia’s own artillery, while placing the Russian batteries at risk.
It also could threaten Russian supply depots, amid western belief that the Russian forces suffer logistical problems.
Some analysts have said Himars can be a “game-changer” in the war at a time when Ukraine forces appear to be struggling under Russian artillery fire.
But others say Himars will not suddenly turn the tables. “The Himars would even the playing field,” a senior US defence official said.
Why is Washington limiting the range?
The US president wrote in the New York Times that the advanced rockets will enable the Ukrainians “to more precisely strike key targets on the battlefield in Ukraine”.
Yet the US plans to limit the range of the missiles it gives Ukraine to avoid them being used to hit targets deep inside Russia.
“We are not going to send to Ukraine rocket systems that can strike into Russia,” Biden said.
Since Russia invaded on 24 February, the US has been sensitive about taking any action to support Kyiv that might provoke Moscow to take the war beyond Ukraine’s borders.
That has included not overtly backing Ukraine strikes inside Russian territory. Several times Ukraine has used its own rockets, drones and helicopters to hit nearby Russian targets in neighbouring Kursk and Belgorod oblasts.
If the US provided ATACMS, they would theoretically have the ability to strike major Russian urban centres and military bases, including airfields from where attacks on Ukraine are launched.
“[The] Ukrainians have given assurances they will not use these systems against Russian territory,” a US official said.