Last Sunday, as Russia put pressure on Ukrainian forces across a 600-mile front line, Ukraine received a shipment of anti-armor rockets, missiles and badly needed 155-millimeter artillery shells. It was the first installment from the $61 billion in military aid that President Biden approved just four days earlier.
A second batch of those weapons and ammunition arrived on Monday. And a fresh supply of Patriot interceptor missiles from Spain arrived in Poland on Tuesday. They would be at the Ukrainian front soon, a senior Spanish official said.
The push is on to move weapons to a depleted Ukrainian army that is back on its heels and desperate for aid. Over the last week, a flurry of planes, trains and trucks have arrived at NATO depots in Europe carrying ammunition and smaller weapon systems to be shipped across Ukraine’s borders.
“Now we need to move fast, and we are,” Mr. Biden said on April 24 when he signed the bill approving the aid. He added, “I’m making sure the shipments start right away.”
But it may prove difficult for Mr. Biden and other NATO allies to maintain the urgency. Weapons pledged by the United States, Britain and Germany — all of which have announced major new military support over the last three weeks — could take months to arrive in numbers substantial enough to bolster Ukraine’s defenses on the battlefield, officials said.
That has raised questions about Ukraine’s ability to hold off the Russian attacks that have had Kyiv at a disadvantage for several months.
Yet there is little time for Ukraine to lose against a steady Russian advance.
Avril D. Haines, the director of U.S. national intelligence, told Congress on Thursday that Russia could potentially break through some Ukrainian front lines in parts of the country’s east. A widely anticipated Russian offensive this month or next only adds to the sense of gravity.
“The Russian army is now trying to take advantage of the situation while we are waiting for deliveries from our partners, primarily the United States,” President Volodymyr Zelensky of Ukraine said on Monday at a news conference in Kyiv with the NATO secretary general, Jens Stoltenberg.
He noted that “some deliveries have already been done” but added, “I will only say that we haven’t gotten all we need to equip our brigades.”
Mr. Stoltenberg also sounded impatient. “Announcements are not enough,” he said. “We need to see the delivery of the weapons.”
A confidential U.S. military assessment this week concluded that Russia would continue to make marginal gains in the east and southeast leading up to May 9, the Victory Day holiday, a senior U.S. official said. However, it concluded that the Ukrainian military would not collapse completely along the front lines despite the severe ammunition shortages, the official said.
Other American officials do not believe Russia has the forces to make a major push before May 9, a day Moscow usually uses to show off its military might. That would require a large buildup of forces that American officials so far have not seen.
The officials interviewed for this article spoke on the condition of anonymity to discuss sensitive military and intelligence assessments as well operational details.
American and European officials described the effort to send weapons to Ukraine as an uptick from the modest but steady trickle of aid from allies over the last six months.
Some of the new weapons began arriving even before they were announced. A British defense official said that parts of the estimated $620 million in aid that Prime Minister Rishi Sunak unveiled on April 23 — Britain’s largest single military infusion to Ukraine so far — began moving weeks ago.
But it could take weeks for the arrival of additional shipments of long-range Storm Shadow missiles, which the British official described as “an absolute priority.” The official would not be more specific, citing security concerns, and spoke on the condition of anonymity to describe the sensitive delivery process.
Senior U.S. and other Western officials agreed that artillery, air defense interceptors and other ammunition were Ukraine’s most pressing needs. They are also among the weapons that can be delivered more quickly: flown to depots by military aircraft and then sent over the border in trains or trucks, packaged in pallets that are easy to conceal.
The pace has picked up, defense officials said, at Rzeszow-Jasionka Airport in southeast Poland, around 50 miles from the Ukraine border, since Congress approved the aid.
Deliveries can be especially quick if the ammunition is already stockpiled in central and Eastern Europe, where the United States and other allies keep reserves.
It can take as little as a few days for logistics specialists at a U.S. military base in Wiesbaden, Germany, to coordinate delivery for the most urgently needed arms, officials said.
Combat vehicles, boats, sophisticated cannons, missile launchers and air defense systems are much more difficult and take longer to transfer — in part because their size often requires them to be shipped by sea and heavily guarded trains.
One American official said most of the larger weapons that were financed by the new U.S. aid, and even some of the ammunition, would be shipped from the United States and most likely not be delivered until well into the summer — or even later. The U.S. official also spoke on the condition of anonymity.
Complicating matters, not all the weapons that have been promised are immediately available.
The U.S. official noted that it would take time to sort out which items could be given to Ukraine without depleting NATO units that need to be combat-ready, such as those that use Bradley infantry fighting vehicles and Humvee personnel carriers that were part of the American package. Other arms, like the 155-millimeter artillery rounds that Ukraine desperately needs, are in short supply worldwide.
And Ukrainian troops need training to use some weapons before they can be transferred, like the third German donation of a Patriot system that was announced on April 13.
On Monday, around 70 Ukrainian troops will begin a six-week course on the Patriots at an air base in eastern Germany. That is accelerated from the six-to-nine-month course that German air forces generally undergo, said Col. Jan-Henrik Suchordt, the branch head of surface-based air and missile defenses at Germany’s Air Force headquarters.
“You can’t just give away a weapons system like Patriot without training the people on how to use it,” Colonel Suchordt said in an interview on Thursday.
Once the training is completed, it usually takes German forces about two days to truck the huge missile launchers, radar and other parts to the logistics hub in Poland and to give them to Ukrainian officials to take across the border.
The newly pledged Patriot system is not expected to arrive in Ukraine until late June at the earliest. Its delivery could coincide with shipment of another major weapon system Ukraine has long demanded: F-16 fighter jets. Though Ukraine has been asking for the warplanes almost since the start of the war in February 2022, they are not expected to be delivered until this summer — and only in small numbers initially.
As Ukraine struggles to hold on to territory, U.S. officials believe that Russia will continue to attack and press the advantages it has now, before all the Western reinforcements are delivered.
“I don’t think the Russians intended to make the big push now, but they’ve had tactical successes in a few places and are likely rushing to exploit them before the influx of renewed munitions reach the front to make the difference,” said Ralph F. Goff, a former senior C.I.A. official who served in Eastern Europe and the former Soviet Union and who recently visited Ukraine.
He cautioned that threats last week by the Russian defense minister, Sergei Shoigu, about increased attacks on logistics centers and storage facilities for Western weapons in Ukraine should be taken seriously.
This week, soldiers from several Ukrainian brigades across the front lines expressed great relief that more Western weapons were on the way but said they had yet to see any of the vitally important artillery shells and other equipment needed for the day-to-day battles.
It remains to be seen how much Russia can exploit its current advantage before Western supplies arrive. Even securing the entire Donbas region remains a formidable challenge for Moscow, with battles for the large cities under Ukrainian control likely to be long and bloody.
Yet Western leaders and defense officials nearly unanimously agree that Ukraine is facing a particularly fraught moment — distinguishable even within the grim arc of the two-year war — that demands urgency in weapon deliveries.
“Are there more threats? There are,” Mr. Sunak said in Poland, announcing the new British aid on April 23.
“We can’t be complacent,” Mr. Sunak warned.
Helene Cooper and Nastya Kuznietsova contributed reporting.
