Russian forces are razing the already battered city of Avdiivka in eastern Ukraine to the ground and sending waves of assault units to overwhelm outgunned Ukrainian troops. After months of brutal fighting, the Russian military is threatening to cut off a vital supply line to the city, which could render further defense impossible.
As Gen. Oleksandr Syrsky assumes his role as Ukraine’s top military commander — after a broad shake-up of army leadership on Thursday — he could soon be confronted again with the grim calculus that has been a feature of the two-year war: When does the cost of defending ground outweigh any benefit gained by inflicting pain on the enemy?
It is a bloody equation that General Syrsky has had to try to work out many times as the commander of ground forces in eastern Ukraine, and it is one that critics — including American military officials — contend he has not always gotten right, particularly in the battle for Bakhmut.
Assessing that strategy will be only part of the “renewal” that President Volodymyr Zelensky said was necessary when he dismissed his commanding general, Valery Zaluzhny, on Thursday and named General Syrsky to replace him. Mr. Zelensky also named five generals and two colonels he intends to promote as part of the sweeping overhaul.
Ukraine’s military challenges go well beyond any single battle. American assistance, urgently needed, remains in doubt. Ukrainian troops are exhausted, and they lack weapons and ammunition. Air defense systems, crucial to protecting civilians from Russian missiles, are being steadily exhausted by repeated bombardments.
American officials assess that, without replenishment, Ukraine has enough air defenses to last until only next month.
And Russia’s president, Vladimir V. Putin, delivered a blunt message Thursday night in an interview with Tucker Carlson, saying that Ukraine would not regain territory and that it was time to make a deal.
Western military analysts have suggested that 2024 will be a rebuilding year for Ukraine, and General Syrsky will need to figure out how best to employ soldiers to hold back Russian offensives while generating new and effective fighting forces.
Before Ukraine’s leaders think of regaining ground, though, they must first hold what they have — and preventing Russian advances is complicated by critical shortages of soldiers and ammunition.
Western officials and military experts have warned that without U.S. assistance, a cascading collapse along the front is a real possibility later this year.
It would still be at least a couple of months before the lack of renewed aid has a widespread impact, they say. But without it, they add, it’s hard to see how Ukraine will be able to maintain its current positions on the battlefield.
By next month, Ukraine could struggle to conduct local counterattacks, and by early summer, its military might have difficulty rebuffing Russian assaults, the officials and analysts say.
However, officials also assess that Russia would struggle to quickly build enough capability to conduct a major offensive across eastern Ukraine. Instead, the Russian forces would most likely move forward in a clumsy disjointed way but with a high threshold for casualties among their own troops.
On Friday, the Kremlin dismissed the Ukrainian leadership change as inconsequential. “We don’t believe this is a factor that can change the course of the special military operation,” Mr. Putin’s spokesman, Dmitri S. Peskov, told journalists, using Moscow’s phrase for the war. “It will continue until all of its goals are achieved.”
Still, Ukraine has managed to fend off doomsday scenarios in the past, most notably when it drove Russian forces from Kyiv in the first months of the war.
The Pentagon said on Friday that the chairman of the Joint Chiefs of Staff, Gen. C.Q. Brown Jr., spoke with General Syrsky on his first full day on the job, and discussed “the latest battlefield assessments.”
In his first public comments since his appointment, General Syrsky said that his immediate priority would be “the fastest and most rational distribution and delivery of everything necessary for combat units” to counter Russian assaults.
He vowed to put troops’ “lives and health” at the forefront of battlefield decisions, working to maintain “a balance between fulfilling combat missions and restoring units.”
With his comments, General Syrsky may have been responding to critics who say that he has been too willing to sacrifice soldiers to achieve questionable military goals.
In announcing the overhaul on Thursday, Mr. Zelensky also spoke of the need to address the needs of soldiers in the cauldron of battle. While there are almost a million people in the military, Mr. Zelensky said, “the majority of them have not felt the front line in the same way as the minority who are actually at the forefront, actually fighting.”
“This means that we need a different approach to rotations in particular,” he said. “A different approach to frontline management. A different approach to mobilization and recruitment. All this will give more respect to the soldier. And restore clarity to actions in the war.”
But Mr. Zelensky offered little detail about how the overhauled leadership would meet his goals, and he did not explain where the previous commander’s team had fallen short.
Mr. Zelensky’s critics say that he has avoided making politically unpopular decisions and that he has failed to address the challenges surrounding efforts to overhaul and reinvigorate the mobilization process.
General Syrsky is something of divisive figure within the military, viewed by some as too close to the Zelensky team to challenge misguided political decisions.
But he is intimately familiar with the often byzantine bureaucracy of the Ukrainian armed forces, and he has participated in most of the important command decisions during the war.
He will now have to expand his field of vision from the bloody battles in eastern Ukraine to a sprawling war being fought on land, air and sea. He has long experience commanding conventional forces, but unconventional warfare will take on an increasingly important role as Ukraine seeks to make up for its disadvantages by waging an asymmetric campaign — including striking inside Russia.
Beyond the tactical and strategic decisions, General Syrsky must also maintain morale among the troops during one of the most trying moments of the war. That includes winning over soldiers who liked and respected his predecessor, General Zaluzhny.
Mr. Zelensky also appointed Maj. Gen. Anatoliy Barhilevych as Ukraine’s new chief of the General Staff, replacing Lt. Gen. Serhiy Shaptala. The move was expected as General Syrsky fills out the staff who will work closely with him on a day-to-day basis.
General Zaluzhny is widely regarded as a heroic figure who helped save his country in its darkest hour and earned a reputation for compassion even as he made difficult choices. On Friday, Mr. Zelensky awarded the general the title Hero of Ukraine.
Oleksandr, a 27-year-old soldier fighting on the front who, like others in this article, asked to be identified by only his first name in line with military policy, said, “In the million-strong army, there are and will be problems, countless problems, but here we are talking about trust.”
“General Zaluzhny has had — and continues to have — unquestionable authority and trust from both the military and society,” Oleksandr added. “The president did not clearly explain to society the reasons for General Zaluzhny’s resignation.”
Other soldiers, however, seemed to take the change in stride. Viy, a 43-year-old battalion commander, said that Generals Zaluzhny and Syrsky might have different management styles but results were all that counted.
“In the big picture, during two years of war, when you are constantly working at a very high pace, especially for military personnel, you don’t pay much attention to the high echelons of power,” Viy said.
Victor, a 45-year-old sniper, said that the decision did not come as a surprise given the very public tensions between Mr. Zelensky and General Zaluzhny.
“We’re soldiers, and we can’t afford to fall into the depression and panic that partially sweeps through the civilians now,” Victor said.
He also expressed concern that the Russians would try to exploit the change, but he said that soldiers had little time to think about political machinations.
High-level strategy is important, he added, but the war is being fought by “ordinary guys in trenches and cities.”
“Skilled commanders at the level of companies and battalions, that’s who wins the war,” he noted. “Whether Syrsky or someone else comes, they’ll fight just the same. You can’t build an army around one person.”
Reporting was contributed by Maria Varenikova, Liubov Sholudko and Oleksandr Sushko from Kyiv; Julian E. Barnes from Washington; and Ivan Nechepurenko from Tbilisi, Georgia.
