The United States announced on Tuesday that it was sending multiple rocket launcher systems to Ukraine, but its ability to make a real game-changer on the ground against the Russian military is not so clear.

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The announcement concerns Himars, a mobile rocket launcher system -- mounted on light armor -- that can fire many missiles at the same time.

The Russian and Ukrainian armies already use similar tools, but the American Himars systems have a longer range and are more accurate.

Those that will be delivered to kyiv this time have a range limited to around 80 km, according to a senior White House official. Washington did not want the Ukrainian army to be able to fire on targets in Russian territory.

“We are not going to send rocket systems to Ukraine that can hit inside Russia,” Joe Biden told reporters Monday morning.

What weapons are these?

The M142 Himars systems are a modernized, slimmed down, lightly armored version of the chain-mounted M270 MLRS developed in the 1970s by the United States and its allies.

Himars can carry two types of missile launch stations: one allows six 227 mm guided missiles to be launched at the same time, the other a single ATACMS tactical missile, with a longer range.

A small team can reload the missiles alone in minutes. This will require training of Ukrainian soldiers.

The US Army has Himars already stationed in Europe. Poland and Romania, members of NATO, also have them.

The quantity that Washington plans to send to Ukraine has not yet been specified.

Why are they so expected?

The American multiple rocket launchers will allow the Ukrainian armed forces to strike in depth the Russian positions while placing their batteries further from the front.

The missiles fired by six from the Himars are GPS-guided and have a range about twice as high as that of the conventional shell guns already supplied by the United States, the M777 Howitzer.

This range makes it possible to place the batteries out of range of the Russian artillery while being able, conversely, to strike them.

These missiles could also bomb Russian army logistics depots far behind their lines.

But the United States will not supply kyiv with the ATACMS tactical missiles, which have a range of 300 km.

For specialists, the Himars could change the military balance of power on the ground, while the Ukrainian army seems to be retreating in the Donbass in the face of Moscow's firepower.

Other analysts prefer to remain more cautious about the impact of such a weapon after more than three months of war.

"The Himars would rebalance the balance of power," said a senior American official.

Why is Washington limiting their reach?

Since the beginning of the Russian invasion on February 24, the United States has helped Ukraine while avoiding at all costs taking any action that could be seen as a provocation by Russia - for fear that the conflict could spread beyond the borders of Ukraine.

This has resulted in particular in the refusal to openly endorse Ukrainian strikes within Russian territory. With missiles, drones and helicopters, kyiv forces have already carried out attacks in neighboring Russian provinces.

If Washington had decided to deliver the long-range ATACMS missiles with Himars systems, kyiv could theoretically have targeted major Russian cities and military centers, including air bases used to attack Ukraine.