CNN  — 

The Russian flag has been raised in several parts of the eastern town of Avdiivka in Donetsk, hours after Ukrainian forces beat a hasty retreat from the ruins of a town they’ve been defending for a decade.

But Ukraine’s army is under pressure at several other points along the frontline that meanders for some 1,000 kilometers from the border with Russia in the north to the Black Sea.

The Russian military may have sensed a window of vulnerability in its adversary. Ukraine’s better units are exhausted after two years of combat; there is a new commander-in-chief, Oleksandr Syrskyi; and Ukrainian troops are short of shells and vulnerable to relentless air strikes.

While the goal of President Volodymyr Zelensky and the armed forces is to recover all illegally occupied territory, the Ukrainians are now struggling to prevent the Russians from adding to the approximately 18% of Ukrainian territory they already hold.

President Vladimir Putin’s declared aim is to seize all of the eastern regions of Luhansk and Donetsk, but few believe he will stop there if there are further opportunities.

The Russians launched a determined drive to seize Avdiivka in October. But they are also on the attack near Bakhmut and Mariinka (also in Donetsk), and towards Kupiansk in the north.

On the southern front, in Zaporizhzhia, Russian and Ukrainian sources speak of a massive Russian build-up in the area where the Ukrainians tried to launch their counter-offensive last summer. According to some analysts a force of 50,000 men has been assembled.

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The daily update from the Ukrainian military provides a glimpse of the firepower now being brought to bear by the Russians. On Saturday alone, according to the General Staff,  there were 82 combat engagements. “The enemy launched a total of 13 missile and 104 air strikes, firing 169 times from multiple launch rocket systems at Ukrainian military positions and residential areas.”

The update is full of words like “repelled” and “held back,” as Ukrainian units in Kharkiv, Donetsk and Zaporizhzhia regions cling to their defensive positions.

Ivan Tymochko, Chairman of the Reservists Council of Ukrainian Land Forces, said Saturday that “despite the fact that our attention is focused on Avdiivka, in fact, very intense fighting is ongoing in the Lyman-Kupiansk sector, [and] near Bakhmut. The enemy has sharply amassed forces in the area of Robotyne,” another flashpoint area on the southern front.

The Ukrainians are trying to establish new defensive positions north of Avdiivka on higher ground. Analysts do not expect an immediate Russian assault on these lines, as troops regroup, but they may take some outlying villages.

The destruction caused by Russian artillery and air strikes over several months in Avdiivka essentially left the Ukrainians with no cover. The same Russian approach – to obliterate everything in the way – eventually worked in 2022 in the cities of Severodonetsk and Lysychansk.

One soldier in the area, Yehor Firsov, told Ukrainian TV on Saturday: “Just think: what is our [small] FPV drone against a 500 kg or a huge 1-tonne bomb that hits a building and destroys it? This is how the enemy gained the advantage, destroying everything and advancing in the city.”

Anatolii Stepanov/AFP/Getty Images
Ukrainian servicemen build a temporary fortification near Avdiivka.

Having taken what remains of the town, the Russians may release some units to reinforce attacks on the ruins of nearby Mariinka. In recent days they have made ground to the south of the town, and Ukrainian defenses in the direction of Vuhledar are now under intense pressure. The Ukrainian military reported Sunday that over the previous day, the Russians “made 23 attempts to break through our defenses.”

The Russian goal to the west and north-west of Bakhmut is the small town of Chasiv Yar, which sits on commanding heights within artillery range of the towns of Kramatorsk and Kostiantynivka. Last week, the spokesman for the Ukrainian military in that area, Illia Yevlash, said that on one day, the Russians had shelled Ukrainian positions more than 600 times.

“We need more shells, thousands and thousands of shells, especially 155 mm ones,” Yevlash said. “The enemy is trying to attack from the flanks. They are using small assault groups, as heavy equipment cannot move across the fields due to icy conditions and impassable roads.”

Ukraine still holds nearly half of the Donetsk region, whose seizure has been a consistent goal of President Vladimir Putin’s invasion. It took the Russians months to capture just 30 square kilometers in and around Avdiivka.

Diego Herrera Carcedo/Anadolu/Getty Images
Ukraine still hopes to recapture the territory it lost to Russia but is under pressure across the frontlines.

In the south, the first Russian probing of Ukrainian lines has already begun. According to the Ukrainian military, three Russian tanks were destroyed Saturday and dozens of soldiers killed amid a Russian offensive that “involved 30 pieces of equipment and a fairly large number of enemy personnel,” in more than a dozen attempts to break through Ukrainian lines.

“There were no losses of positions in the Zaporizhzhia sector. The enemy suffered significant losses. We are holding back the enemy’s offensive.”

But Russian military bloggers had a different take, saying that Russian 42nd and 76th divisions had advanced some two kilometers near the village Robotyne, which the Ukrainians took last summer, and had pummelled Ukrainian defensive positions with artillery and air strikes.

Here as elsewhere, the Russians have vastly increased their use of 500-kilogram glide bombs from aircraft against which Ukrainian front-line troops have little protection.

One Russian blogger, ‘Archangel Special Forces Z’, claimed that “airborne troops are conducting a powerful artillery preparation in Zaporizhzhia direction! There are already assault operations underway in some areas.”

Amid what is a tough outlook for Ukrainian troops on the frontlines, the Russians are losing an extraordinary number of men killed or wounded.

President Volodymyr Zelensky said Saturday that in Avdiivka, seven Russians were being killed for every Ukrainian soldier lost.

The Ukrainian military command claimed that it had inflicted “losses of 20,018 personnel, 199 tanks, and 481 armored combat vehicles” in the region from Avdiivka through western Zaporizhzhia between January 1 and February 15.

While that cannot be confirmed, US officials have previously said that the Russians were suffering heavy losses because of poor tactics.

But the Russian way of war has long been to send thousands more into battle, regardless of losses, and their reservoir of military manpower is much greater than the Ukrainians’.

At present, with Ukraine short of weapons and munitions because of the US Congress’ not passing a $60 billion package of aid, the Russians are also making their very substantial advantage in artillery, armor and airpower felt.