Over the past several weeks, Russian troops have slowly expanded their control of territory in the Donbas, pounding Ukrainian defense forces with artillery bombardments and reducing towns and villages to rubble.
Setbacks for the Ukrainian military in the east contrast with the course of the war in the weeks after Russia’s February 24 invasion, when Kyiv's forces kept the attacking troops out of the capital and other key cities, picking off Russian tanks with anti-armor weapons.
Russia has since concentrated its forces in the east for a large-scale artillery fight reminiscent of World War II battles. Experts say Moscow hopes to take advantage of having the upper hand in terms of manpower and weapons, something visible in its nonstop bombardments of Ukrainian forces in the Donbas in recent days.
Now the West is taking steps to arm Ukraine for the new reality of the war before it is too late. On June 1, U.S. President Joe Biden’s administration formally announced a new tranche of military aid totaling $700 million that includes powerful high-mobility artillery rocket systems (HIMARS) capable of pulverizing enemy forces from miles away.
Likening the artillery war in the Donbas to two boxers slugging it out in the ring, a senior NATO official said on condition of anonymity on May 30 that the outcome will depend on "who has more rounds of artillery ammunition, who has more rockets, who has more people to actually put on the ground in the fight."
With Russia close to capturing the whole of the Luhansk region, one of two provinces that make up the Donbas, the West is hoping to change the tide of the fighting. Russian President Vladimir Putin has made capturing the Donbas a key military aim.
Russia currently has about 110 battalion tactical groups (BTGs) in Ukraine, according to the United States. Each group could have six to eight artillery pieces such as howitzers or rocket launchers, Mark Cancian, a retired U.S. Marine colonel and a senior adviser at the Washington-based Center for Strategic and International Studies, told RFE/RL, an estimate that would put the total as high as 900, with the majority concentrated in the Donbas.
Wesley Clark, NATO’s supreme allied commander in Europe from 1997 to 2000, warned last week that Ukrainian forces lack the artillery to fight the new phase of the war effectively and said Western military aid was so far "insufficient" to drive the Russian forces back.
"Ukraine needs to be further reinforced. It has the fighting capacity and the determination to force the Russians out; it does not have the means," he told RFE/RL in an interview on May 27.
"This is a fight that could be lost," he said.
Ukraine's military industry has been partially crippled by missile attacks since Russia launched the full-scale invasion, undermining its defense capabilities.
And the Ukrainian military is also lacking ammunition for its Soviet-made artillery, including its 152-milimeter howitzers, hindering its ability to destroy Russian weapons.
Globally, the largest suppliers of such ammunition are Russia and China, according to Cancian. "The United States has literally been scouring the world to find Soviet-standard ammunition to give to the Ukrainians. And my suspicion is that we're running out of places that will sell us that kind of ammunition," he said.
For weeks, as its soldiers were slowly pushed back from some of their positions in the Donbas, Ukraine had been asking Western nations for greater military aid, including howitzers and rocket launchers to destroy Russian artillery.
In a guest essay in The New York Times on May 31, Biden wrote that his administration had agreed to provide Ukrainian forces "with more advanced rocket systems and munitions that will enable them to more precisely strike key targets on the battlefield in Ukraine."
However, he added that the United States was "not encouraging or enabling Ukraine to strike beyond its borders."
The United States has hesitated to turn over such heavy artillery amid concerns it could provoke Russia, analysts said.
Some analysts say the administration's internal debate on weapons supplies has lost precious time for Ukraine. "All of our decisions have been late," Ben Hodges, a former commander of the U.S. Army Europe, told RFE/RL.
"The administration has overexaggerated the concern that whatever we do might provoke the Russians. They don't need provocation. They attack without provocation," he said. "We've lost weeks when [rocket systems] could have been delivered," added Hodges, who is now a military analyst for the U.S.-based Center for European Policy Analysis.
Ukrainian President Volodymyr Zelenskiy told his nation on May 30 that the situation in the Donbas was "extremely difficult," saying Russia had concentrated its military's "maximum combat power" in the region. Earlier in May, he said Russian attacks were killing from 50 to 100 Ukrainian soldiers a day.
That intense bombardment is putting Ukrainian supply lines under extreme pressure, making it difficult to get Western weapons quickly to the soldiers at the front line, analysts said.
Western military aid is brought into Ukraine from Poland by train and taken further by truck to the front lines. Russia is seeking to cut off those transport links to the Donbas.
Hodges said Ukrainian forces will face a few "pretty rough" weeks before they start feeling the "positive effect" from all the U.S. and other Western artillery starting to arrive.
Clark sees a two-month window starting in July for Ukrainian forces to drive the Russians out of the Donbas if they receive enough heavy artillery.
By then the ground will be parched, making it easier to attack, while Russia will have yet to mobilize more forces, he said.
Menu Of Weapons
The United States began sending heavy artillery to Ukraine in April, including the powerful M777 howitzer, which can strike targets as far as 40 kilometers away.
On May 26, a senior U.S. Defense Department official said it had delivered 85 M777 howitzers to Ukraine, as well as 190,000 projectiles for use in those weapons systems.
The Biden administration has promised a total of 108 M777s and 209,000 projectiles, though that could be increased as the war goes on.
The howitzers can fire a variety of 155-milimeter projectiles including guided munitions, which Cancian said were a "potential game changer" in the Donbas fight because it has greater potential of hitting and destroying Russian artillery.
It is unclear how many guided projectiles for the M777 Ukraine has received.
Cancian says it takes time to train soldiers to operate and maintain howitzers, calling it a "constraint" on their quick deployment to the front lines.
The United States has trained more than 400 people to operate the M777 and about 50 have learned to maintain them, the U.S. official said. Eight soldiers are required to operate an M777.
The HIMARS just approved by the Biden administration are just as devastating. Glen Howard, a military expert and president of the Jamestown Foundation, said HIMARS can "pulverize" an area where enemy forces are gathering for an attack. "They just saturate an area," he said.
The HIMARS consists of a pod of six rockets launched from a truck. Unlike the howitzer, which can fire continuously, it takes about five minutes to reload a pod.
The HIMARS and the howitzers "complement each other," Cancian said. "If you want to smother a target at long range, [HIMARS are] excellent. On the other hand, if you want to keep firing at some enemy position to make them keep their heads down or try to destroy it with a lot of ammunition, artillery cannon is great."
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The United States has authorized the delivery of four HIMARS along with rockets capable of traveling up to 70 kilometers, Colin Kahl, undersecretary of defense for policy, said on June 1. The United States may ship additional HIMARS to Ukraine as needed, but troops must first learn how to use them, a process that will take about three weeks, he said.
Kahl warned the HIMARS were no silver bullet, saying that "no system is going to turn the war. It is a grinding, hard conflict."
HIMARS can launch missiles as far as 300 kilometers -- but delivering missiles with such a range might violate Biden's determination not to encourage Ukraine to target Russian soil.
"The Biden people are obsessed with something being offensive, because it means escalation," Howard said regarding the limitation. "And that's why the [M777 munitions] were so slow in arriving."
Howard suggested the HIMARS along with new Western anti-ship missiles could potentially deter Russia from attacking ships exporting grain from Ukraine's Black Sea ports.
Russia is currently blockading Ukrainian ports, driving up grain prices and raising concerns about a global famine.
Its warships and submarines are patrolling the waters between Crimea and Snake Island, a small rocky outpost just 48 kilometers from Ukraine's shore.
Denmark has recently delivered Harpoon anti-ship missile systems to Ukraine to bolster its low supply of domestic weapons.
Ukraine claims to be responsible for the April sinking of the Moskva, the flagship of the Russian Black Sea Fleet.
Russia, which captured Snake Island earlier in the war, is placing air- and missile-defense systems there in an attempt to hold the strategic outpost.
While the HIMARS rockets approved by the Biden administration cannot reach Russian artillery on Crimea, they can reach Snake Island.
It is unclear whether Ukraine will place the HIMARS along its Black Sea coast.