LONDON — Instead of sending a rush of troops to Avdiivka to subdue the Ukrainians who control the frontline town, Russian forces earlier this month began sending only a few soldiers at a time.

Two or three Russians would assault Ukrainian positions inside the city, followed about half an hour later by another two or three. In those increments, they began to dominate Ukrainian positions “step by step,” according to Andrii Teren, a Ukrainian commander.

“We had the impression that these groups had no end, every 20 or 30 minutes we were attacked,” Teren told Rueters earlier this week. “That’s why it became so difficult for our infantry.”

PHOTO: Ukrainian servicemen of the 47th brigade are seen in their positions on the front line, amid Russia's attack on Ukraine, near the town of Avdiivka, recently captured by Russian troops in the Donetsk region, Ukraine, on February 20, 2024.

Ukrainian servicemen from the 47th Brigade are seen in their positions on the front line, amid Russia’s attack on Ukraine, near the town of Avdiivka, recently captured by Russian troops in the Donetsk region, Ukraine, on February 20, 2024.

Inna Varenytsia/Reuters

The difficulties Teren described echoed those described by other frontline Ukrainian commanders. He said he didn’t have enough staff. He, too, did not have enough shells if the Russians maintained their slow attack. He said they simply “exhausted” his troops.

As Russia’s war in Ukraine turns two years old on Saturday, Russia is on the attack again, attacking cities along the front line. Those attacks come at a time when international aid to kyiv has been reduced, meaning Ukrainian weapons stockpiles are getting smaller.

“Russian forces have intensified attacks at several points along the front line over the past week, probably with the intention of straining Ukrainian forces,” the UK Ministry of Defense said on Wednesday.

Russian Defense Minister Sergei Shoigu said Russian forces had taken full control of Avdiivka, touting it as a strategic breakthrough. While Ukrainian President Volodymyr Zelenskyy acknowledged that his forces had withdrawn, he said the move had been tactical.

PHOTO: Ukrainian President Volodymyr Zelenskyy and Commander of the Ukrainian Ground Forces, Colonel General.  Oleksandr Syrski, right, looks at a map during his visit to the frontline city of Kupiansk, Kharkiv region, Ukraine, Nov. 30, 2023.

Ukrainian President Volodymyr Zelenskyy and Commander of the Ukrainian Ground Forces Colonel-General. Oleksandr Syrski, right, looks at a map during his visit to the frontline city of Kupiansk, Kharkiv region, Ukraine, Nov. 30, 2023.

Efrem Lukatsky/AP

“Saving our lives is also, in my opinion, the right decision,” he said of the February 17 retreat in Munich. “Then there will be recovery, they will wait until they have adequate weapons, which were simply insufficient.”

The loss of Avdiivka came after months of Ukrainian officials raising the alarm about dwindling military reserves. The United States has provided at least $44.9 billion to kyiv, but if Congress does not approve a new aid package by late spring or early summer, the situation in Ukraine could become dire, US officials told ABC News.

As of December 2023, the United Kingdom had pledged about £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 euros, or about $6.1 billion, which included funding for weapons.

PHOTO: A Ukrainian soldier stands guard looking for Russian drones in the sky in the Zaporizhzhia region, January 30, 2024. After Kiev's counteroffensive failed to break through Russian lines last year, kyiv went on the defensive.

A Ukrainian soldier stands guard looking for Russian drones in the sky in the Zaporizhzhia region, January 30, 2024. After Kiev’s counteroffensive failed to break through Russian lines last year, Kiev went on the defensive, building its own lines. protection to thwart a possible Russian offensive.

Roman Pilipey/AFP via Getty Images

But promises of funding for ammunition and weapons have become scarcer as the war has progressed. The European Council earlier this month approved €50 million in aid for the besieged nation, although that money went not for ammunition but rather to finance the Ukrainian government, allowing it to pay 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. Last spring, Ukrainian forces launched a long-awaited counteroffensive, attempting to push back toward Crimea, the southern peninsula annexed by Russia in 2014.

The counteroffensive initially gained momentum slowly. It led to some advances near Donetsk, although it caused heavy Ukrainian casualties and failed to sever Russia’s land bridge to southern Ukraine.

PHOTO: A woman reacts as she commemorates a family of two adults and three children, local residents who were killed on Friday, February 9, in their home that burned in a Russian drone strike, amid the Russian attack, in Kharkiv, Ukraine, February.  12, 2024.

A woman reacts as she commemorates a family of two adults and three children, local residents who were killed on Friday, February 9, in their home that burned in a Russian drone strike, amid Russia’s attack on Ukraine, in Kharkiv, Ukraine, February 2019. 12, 2024.

Vladyslav Musiienko/Reuters

What followed was a fall and winter of intense fighting on the front lines that further depleted Ukrainian arsenals.

Russia also continued its long-range missile and drone attacks on residential areas. Early in the morning it launched attacks on kyiv and Kharkiv, attacking shopping malls, apartment buildings and infrastructure.

PHOTO: A Ukrainian soldier walks inside a newly dug trench that was built as part of a system of new fortifications near the city of Kupiansk, on the front line, in the midst of Russia's attack on Ukraine, in the Kharkiv region , Ukraine, on February 19, 2024.

A Ukrainian soldier walks inside a newly dug trench that was built as part of a system of new fortifications near the town of Kupiansk, on the front line, amid Russia’s attack on Ukraine, in the Kharkiv region, Ukraine , on February 19, 2024.

Sofia Gatilova/Reuters

But another year of tough fighting does not appear to soften the resolve of either Zelenskyy or Russian President Vladimir Putin.

Just like last year, Zelenskyy continues to vow to fight until “every inch of Ukrainian land” is returned to Russian control.

Putin and other Kremlin officials also continued to appear unwavering, although there was at least one high-profile case of defiance by Putin’s inner circle in the second year of the war.

Yevgeny Prigozhin, head of the Wagner paramilitary group and a former ally of Putin, led a chaotic armed rebellion that lasted one day. He sent his forces toward Moscow in June, but then ordered them to retreat. Two months later, Prigozhin died in a plane crash.

PHOTO: Russian President Vladimir Putin listens to Defense Minister Sergei Shoigu during a meeting in Moscow, Russia, on February 20, 2024.

Russian President Vladimir Putin listens to Defense Minister Sergei Shoigu during a meeting in Moscow, Russia, February 20, 2024.

Sputnik/Alexander Kazakov/Pool via Reuters

Earlier this month, veteran 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 post-mortem examination.

The United States will impose “crushing” new sanctions on Russia, including measures to punish the Kremlin for Navalny’s death, officials said.

“Make no mistake,” US President Joe Biden said last week. “Putin is responsible for Navalny’s death.”

“This tragedy reminds us what is at stake right now,” he added. “We must provide funding so that Ukraine can continue to defend itself against Putin’s cruel attacks and war crimes.”

Will Gretsky, Patrick Reevell, Tom Soufi-Burridge, Joe Simonetti, Edward Szekeres, Anne Flaherty, Luis Martinez, Shannon K. Crawford, Justin Gomez and Yulia Drozd of ABC News contributed to this story.

By Sam