Instead of sending a deluge of troops into Avdiivka to overpower the Ukrainians holding the front-line city, Russian forces earlier this month instead began sending in just a few soldiers at a time.
Two or three Russians would storm Ukrainian positions within the city, followed about a half-hour later by two or three others. In those increments, they began to overpower the Ukrainian positions "step by step," according to Andrii Teren, a Ukrainian commander.
"We had the impression that these groups have no end, every 20 or 30 minutes we faced assaults," Teren told Reuters earlier this week. "That's why it became so difficult for our infantry."
The difficulties Teren described echoed those described by other Ukrainian front-line commanders. He said he didn't have enough personnel. Nor did he have enough shells if the Russians kept up their slow-rolling attack. He said they simply "exhausted" his troops.
As Russia's war in Ukraine hits the two-year mark on Saturday, Russia is again on the attack, striking cities along the front line. Those attacks are coming as international aid for Kyiv has slowed, meaning Ukrainian weapons stockpiles are growing ever smaller.
"Russian forces have intensified attacks across several points of the front line within the last week, likely intended to stretch Ukrainian forces," The United Kingdom's Ministry of Defense said Wednesday.
Russia's Defence Minister Sergei Shoigu said Russian forces had taken complete control of Avdiivka, touting it as a strategic breakthrough. While Ukrainian President Volodymyr Zelenskyy acknowledged his forces had withdrawn, he said the move had been a tactical one.
"Saving our lives is also, in my opinion, the right decision," he said of the withdrawal on Feb. 17 in Munich. "Then there will be recovery, they will wait for the proper weapons, which were simply insufficient."
The loss of Avdiivka came after months of Ukrainian officials raising alarms about the military's dwindling stockpile. The U.S. has supplied at least $44.9 billion to Kyiv, but if Congress doesn't pass a new aid package by late spring or early summer, the situation in Ukraine could become dire, U.S. officials told ABC News.
MORE: US estimates Ukraine military shortages could grow catastrophic by late MarchAs of Dec. 2023, the United Kingdom had pledged some £7.1 billion, or about $9 billion, for military assistance, according to a government report. The European Union had also pledged about €5.6 billion, or about $6.1 billion, which included funding for weapons.
But funding pledges for ammunition and weapons have become scarcer as the war has worn on. The European Council earlier this month approved €50 million in aid for the besieged nation, although that money was earmarked not for munitions but for funding the Ukrainian government, allowing it to pay for salaries and services.
The critical situation now described by Zelenskyy and other Kyiv leaders is a far cry from the way the country's military began the second year of the war. Ukrainian forces last spring launched a long-anticipated counteroffensive, in which they attempted to push back into Crimea, the southern peninsula annexed by Russia in 2014.
The counteroffensive initially had a slowly building momentum. It led to some gains near Donetsk, although it brought heavy Ukrainian casualties and it wasn't successful in cutting off Russia's land bridge to southern Ukraine.
What followed was a fall and winter of intense front-line fighting that further cut into Ukrainian stockpiles.
Russia also continued its long-range missile and drone strikes on residential areas. It launched early-morning assaults on Kyiv and Kharkiv, striking malls, apartment buildings and infrastructure.
But another year of hard fighting hasn't seemed to soften the resolve of either Zelenskyy or Russian President Vladimir Putin.
As with last year, Zelenskyy is still vowing to fight until "every inch of Ukrainian land" is returned from Russian control.
Putin and other Kremlin officials also continued to appear unwavering, although there was at least one high-profile instance of a challenge from Putin's inner circle in the war's second year.
Yevgeny Prigozhin, chief of the paramilitary Wagner Group and a longtime Putin ally, led a chaotic one-day armed rebellion. He sent his forces toward Moscow in June, but later ordered them to turn back. Two months later, Prigozhin was killed in a plane crash.
Earlier this month, longtime opposition politician Alexei Navalny became the latest Kremlin critic to die suddenly. He had been transferred to an Arctic prison, where he died of unknown causes, according to prison officials. The Kremlin rejected international calls for an independent postmortem exam.
The U.S. will impose "crushing" new sanctions on Russia, including measures to punish the Kremlin for Navalny's death, officials said.
"Make no mistake," U.S. President Joe Biden said last week. "Putin is responsible for Navalny’s death."
"This tragedy reminds us of the stakes of this moment," he added. "We have to provide the funding so Ukraine can keep defending itself against Putin’s vicious onslaughts and war crimes."
ABC News' Will Gretsky, Patrick Reevell, Tom Soufi-Burridge, Joe Simonetti, Edward Szekeres, Anne Flaherty, Luis Martinez, Shannon K. Crawford, Justin Gomez and Yulia Drozd contributed to this story.