Russia said its forces took complete control Saturday of a city in eastern Ukraine that was the focus of intense combat for months, a development that Moscow could use to boost morale as the second anniversary of its full-scale invasion of Ukraine approaches with the war largely at a stalemate.

The Russian Defense Ministry's announcement came the same day Ukraine’s military chief said he was withdrawing troops from the city of Avdiivka, where the outnumbered defenders had battled a Russian assault for four months.

Russian Defense Minister Sergei Shoigu told the Kremlin that Russian forces were working to clear final pockets of resistance at the Avdiivka Coke and Chemical Plant, officials said in a statement. Videos on social media Saturday appeared to show soldiers raising the Russian flag over one of the plant’s buildings.

Russian President Vladimir Putin sent a personal message of congratulating to his troops in the city, state news agency Tass reported. Kremlin spokesman Dmitry Peskov described Avdiivka’s capture as an “important victory.”

Along with the invasion's upcoming anniversary on Feb. 24, Russia also is preparing for a March presidential election that is all but guaranteed to give Putin another six-year term. The Kremlin has cracked down heavily on dissent during the war, and the death Friday of imprisoned opposition leader Alexei Navalny has silenced the voice of Putin's most formidable foe.

Ukraine is back on the defensive against Russia in the nearly 2-year-old war, hindered by low ammunition supplies and a shortage of personnel. Speaking at the Munich SecurityConference on Saturday, Ukrainian President Volodymyr Zelenskyy warned his country's allies that an “artificial deficit” of arms for Ukraine risked giving Russia breathing space and allowing "Putin to adapt to the current intensity of the war.”

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“Our actions are limited only by ... our strength,” Zelenskyy said, pointing to the situation in Avdiivka after the commander of Ukraine's armed forces said he was withdrawing troops from the city to prevent their encirclement and to save soldiers’ lives.

President Joe Biden said he told Zelenskyy in their Saturday phone call that he remains confident Congress will ultimately approve additional funding for Ukraine. But asked if he was confident more U.S. funding would come through before Ukraine loses more territory, Biden acknowledged, “I’m not.”

“Look Ukrainians have fought so bravely, ” Biden said “There is so much on the line. The idea now when they are running out of ammunition that we’re going to walk away. I find it absurd.”

White House National Security Council spokesperson Adrienne Watson called the withdrawal “the cost of Congressional inaction.”

In a short statement posted on Facebook, Col. Gen. Oleksandr Syrskyi said the Ukrainian troops were moving to “more favorable lines."

“Our soldiers performed their military duty with dignity, did everything possible to destroy the best Russian military units, inflicted significant losses on the enemy in terms of manpower and equipment.

“We are taking measures to stabilize the situation and maintain our positions,” the statement read.

The withdrawal was Syrskyi’s first major test since his appointment this month as Ukraine’s new army chief.

In his previous position as commander of Ukraine’s ground forces, he faced criticism for holding on to the city of Bakhmut for nine months, a siege that became the war’s longest and bloodiest battle and cost Ukraine dearly, but also served to sap Russia’s forces.

In recent days, reports emerged that Ukrainian troops in Avdiivka faced a deteriorating situation.

Rodion Kudriashov, deputy commander of the 3rd Assault Brigade, said Friday that Ukrainian troops were still holding out against the onslaught of about 15,000 Russian soldiers, but he expected the situation would “soon become critical.”

Read: Russia tightens the noose on Ukraine's city of Avdiivka where outnumbered defenders are holding out

“The enemy is trying to penetrate our defense and in some places to bypass our positions,” he told The Associated Press.

The 3rd Brigade said on its social media account Friday that its soldiers were at the huge Avdiivka Coke Plant. Russian warplanes have been dropping about 60 bombs a day, relentlessly shelling the area and launching assaults with armor and infantry, the brigade said.

A video showed dense black smoke over the factory, said to be caused by burning fuel oil reservoirs. The post said: “Poisonous smog spreads all over the plant.”

Russian media reported the Kremlin’s forces were making extensive use of plane-launched glide bombs, which fly at a shallower angle, to batter Ukrainian positions.

Heavily fortified with a web of tunnels and concrete fortifications, Avdiivka lies in the northern suburbs of Donetsk, a city in a region of the same name that Russian forces partially occupy. Capturing Avdiivka could be a timely boost for Moscow and serve as a possible springboard for Russia to drive deeper into the region.

Fewer than 1,000 people remain in the city, according to the Donetsk regional governor, Vadym Filashkin. The city, with a prewar population of about 31,000, is today a bombed-out shell of what it once was.

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Aerial footage of Avdiivka obtained by The Associated Press in December showed an apocalyptic scene and hinted at Russia’s staggering losses, with the bodies of about 150 soldiers — most wearing Russian uniforms — lying scattered along tree lines where they sought cover.

However, the Institute for the Study of War, a Washington think tank, said Thursday that taking Avdiivka would be more of a symbolic win for the Kremlin and would not bring significant changes to the 1,500-kilometer (930-mile) front line that has barely budged in recent months.

“The potential Russian capture of Avdiivka would not be operationally significant and would likely only offer the Kremlin immediate informational and political victories,” the institute said in an assessment.

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“Russian forces would be highly unlikely to make rapid operationally significant advances from Avdiivka if they captured the settlement, and the potential Russian capture of Avdiivka at most would set conditions for further limited tactical gains,” it added.