On May 9, 2014, a 13-ton armored vehicle tore through pro-Russian barricades in Mariupol, launching a young battalion commander into Ukrainian legend as a symbol of raw, improvisational resistance.

Today, that soldier, Maj. Gen. Mykhailo Drapatyi, assumes command of Ukraine’s armed forces in a fraught moment of military and political transition, leading his country in a battle that could have scarcely been imagined a decade ago.

It is a war both of grinding attrition and high-tech innovation, where survival is dictated by which side can adapt faster and better integrate ever-evolving weapons into the daily slog of fighting under skies saturated with drones.

General Drapatyi, 43, who was appointed the top military commander by President Volodymyr Zelensky on Tuesday night, replaced the 60-year-old Gen. Oleksandr Syrskyi. General Drapatyi represents a newer generation of post-Soviet military leadership in Ukraine that has embraced more modern approaches to warfighting.

He is one of the key architects of Ukraine’s “drone line” strategy. Instead of relying purely on static trenches holding vulnerable infantry troops, Ukraine created a continuous “kill zone” behind the front line filled with attack and reconnaissance drones and automated turrets.

That tactic has helped slow Russian advances, allowing Ukraine to take the initiative along parts of the front for the first time in years. It has also given hope to a war-weary nation that has lost tens of thousands of soldiers.

While recent battlefield developments have been positive, especially with long-range strikes in Russia and Crimea, analysts warned that Ukraine must ensure a smooth handover in the military leadership to maintain momentum.

The challenge is heightened by the circumstances of General Syrskyi’s dismissal. Ukraine has been engulfed in turmoil for more than a week, after Mr. Zelensky fired his reform-minded defense minister, Mykhailo Fedorov. Mr. Fedorov, 35, had clashed with General Syrskyi over warfighting strategy, including how far to go in relying on drones and robots.

Protesters took to the streets, viewing Mr. Zelensky’s decision to side with General Syrskyi as a threat to Ukraine’s push for innovation on the battlefield. Through six days of protests, demonstrators moved from calling for Mr. Fedorov’s reinstatement to demanding General Syrskyi’s removal. Mr. Zelensky granted their wish on Tuesday night, choosing as General Syrskyi’s replacement a commander who had endorsed Mr. Fedorov and his vision of modern warfare.

In an online commentary, Mick Ryan, a retired Australian general who is a fellow at the Lowy Institute, a research group in Sydney, wrote that as General Drapatyi assumes his new role as commander in chief, “The danger now is that a change of command creates a period of uncertainty while new leaders find their feet, and Russian forces exploit it.”

“The new team’s first job is to make sure the reshuffle does not slow the tempo of operations at the front, deep inside Russia — or innovation inside the Ukrainian military,” he added.

General Drapatyi steps into a matrix of crises. He must address problems with Ukraine’s recruitment system, while also bracing for a possible renewed Russian mobilization effort. He must shield energy grids from a winter strike campaign even as Ukraine’s most sophisticated air defenses run low on ammunition. And he must blunt Russia’s slow and bloody campaign to level the remaining bastions of defense in the Donbas region of eastern Ukraine.

There is also the crisis in civilian-military structure that was laid bare after Mr. Zelensky fired Mr. Fedorov, a rift between the armed forces and the defense ministry over management of the war effort that their new leaders must work to repair.

It is not clear what role Mr. Fedorov will play going forward, but Mr. Zelensky has offered him other roles in the administration, and the president has said that the two men would meet again on Wednesday.

Mr. Zelensky said that he wanted to give Mr. Fedorov “a worthy leadership position that would allow him to bring together our country’s technological capabilities and ensure their continued development.”

For General Drapatyi, dealing with the president’s office will require a balancing act, analysts said. He will be pulled, they said, between asserting the operational independence favored by military reformers and accommodating Mr. Zelensky’s tendency toward direct battlefield management.

General Syrskyi’s willingness to comply with executive directives made him a predictable partner for Mr. Zelensky. General Drapatyi, by contrast, is taking over with backing from a reformist movement demanding a departure from rigid, top-down command.

Valerii Zaluzhnyi, a former top commander of Ukrainian forces who was fired by Mr. Zelensky in 2024 after the two clashed over mobilization efforts and counteroffensive strategy, said in a statement that the task ahead of General Drapatyi was “much harder than he imagines.”

Taras Chmut, a prominent Ukrainian military analyst, said that the real fight in Kyiv was over defense procurement: what Ukraine buys for the army, with its own money and partners’ money, and who loses income when the process changes.

General Drapatyi, analysts said, will have only limited influence over those decisions and the efforts that Mr. Fedorov had started to overhaul the system to address corruption and refocus purchasing on more modern weapons.

Liudmyla Buimister, an independent lawmaker who is a former special forces commander and still serves in the military, said she expected General Drapatyi to change the culture of the high command, stop the practice of micromanaging battlefield decisions and bring more coherence to the deployment of forces.

General Drapatyi is expected to champion many of the same technology-driven initiatives that Mr. Fedorov was pushing.

Jack Watling, an analyst at the Royal United Services Institute in London, wrote in an online commentary that, with the change at the top, Mr. Fedorov’s push for a data-driven approach to improve the military’s performance might now be possible.

General Drapatyi is also expected to empower commanders who have used technology to reduce casualties.

He advocates giving commanders direct latitude to make real-time decisions based on battlefield conditions. Under General Syrskyi, junior commanders bristled at what they viewed as micromanagement, with the General Staff needing to sign off before troops withdrew from compromised positions or shifted tactics.

General Syrskyi gained a reputation for tolerating high numbers of casualties, though he maintained that protecting soldiers was always his priority.

With the recruitment shortfall, General Drapatyi, like Mr. Fedorov, is believed to see problems in internal processing, training flaws and corruption as primary factors, not a shortage of available men. Ukraine’s hope is that a change in culture in the high command will increase motivation to join the military.

“Already, we are seeing a boost in the morale of the people inside the armed forces and also in the general public,” Ms. Buimister said.

Chief Sgt. Andrii Klymenko, 45, reached by telephone on the southern front, said, “There is a general sense of euphoria, which is creating a kind of hard-to-explain emotional boost in motivation.”

“The euphoria,” he added, “comes from the feeling that a meat-grinder style of command has been replaced, hopefully, by genuine battlefield leadership.”

Liubov Sholudko and Nataliia Novosolova contributed reporting.

President Volodymyr Zelensky of Ukraine removed his top general on Tuesday night amid swelling public protests and growing concerns that the national unity that had helped the country survive nearly five years of war was in danger of fracturing.

The dismissal of the general, Oleksandr Syrskyi, was a major reversal for Mr. Zelensky, who just days earlier sided with him and fired Ukraine’s defense minister, Mykhailo Fedorov.

Mr. Zelensky said he was replacing General Syrskyi with Maj. Gen. Mykhailo Drapatyi, the commander of the Joint Forces. The choice was likely to please the protesters, after Mr. Drapatyi had publicly sided with Mr. Fedorov in his clash with General Syrskyi over warfighting strategy.

Thousands of people had joined mass demonstrations to pressure Mr. Zelensky to change course and reaffirm Mr. Fedorov’s vision of warfare as increasingly dominated by drones and robots. As he championed a military overhaul that leaned into high-tech innovation, Mr. Fedorov, 35, emerged as a symbol of hope to many Ukrainians, particularly young people.

General Drapatyi, 43, is part of a younger generation of Ukrainian officers. After Russia launched its full-scale invasion in 2022, he built a reputation as a frontline commander focused on tactical innovation, drone integration and direct accountability. He is generally highly regarded by rank-and-file soldiers and military reformers alike.

In a statement, Mr. Fedorov called General Drapatyi’s appointment “a breath of fresh air and a new source of hope,” adding that “the voice of change” could “no longer be ignored.”

Mr. Fedorov’s dismissal last week after only six months as defense minister came as Ukraine seemed to finally have regained the initiative in the war, in large part through the increasingly effective use of long- and medium-range drones to strike targets in Russia and Crimea.

Mr. Zelensky said that he had been forced to choose between Mr. Fedorov and General Syrskyi as the differences between their camps had become impossible to resolve.

Ultimately, as the protests grew, it became clear that the rift extended far beyond a clash of personalities. For many Ukrainians, Mr. Fedorov embodied a tech-driven path to victory that might spare lives, while General Syrskyi had come to represent the darkest, most punishing realities of a war fought through sheer attrition.

General Syrskyi, 60, played a crucial role in the defense of Kyiv early in the war and in a counteroffensive in Kharkiv in September 2022. He was appointed commander in chief of the armed forces in February 2024.

In a statement on Tuesday night, Mr. Zelensky praised the general for his service, saying that he had “delivered results” and that “every warrior deserves to be treated with dignity.”

Like many senior Ukrainian commanders, General Syrskyi was trained in the Soviet military system, where personal loyalty was frequently valued over tactical innovation. Critics described him as rigid and out of touch, and he never won widespread public admiration.

During the prolonged and bloody 2023 battle of Bakhmut, General Syrskyi earned the nickname “the Butcher” for his perceived tolerance of high casualties for limited tactical gains. It was a narrative he disputed, saying that preserving soldiers’ lives was his top priority.

Criticism of General Syrskyi erupted almost immediately after Mr. Fedorov was fired. Veterans, analysts and active-duty soldiers accused General Syrskyi of blocking initiatives to adapt to a rapidly changing battlefield. Protesters took to the streets with signs bearing variations of “Fedorov is innovation, old grandpas are degeneration.”

Mr. Fedorov said that the military establishment had resisted procurement reforms that he championed to promote competition and to sever informal ties between the General Staff and politically connected arms manufacturers.

He accused General Syrskyi of maneuvering behind the scenes to preserve his own power and said that instead of defeating Russia, the general had “figured out how to split the country.”

The situation reached a breaking point as dissent within the military spilled into the open.

Last week, General Drapatyi issued a rare public statement supporting Mr. Fedorov, writing, “Silence does not protect the army; it only allows mistakes to accumulate.”

Col. Pavlo Yelizarov, a deputy commander of the air force, submitted his resignation, calling Mr. Fedorov’s removal “a great blow to the country’s defense.”

Faced with this deepening turmoil, Mr. Zelensky met with brigade commanders to hear their concerns. His office urged patience at home while seeking to reassure allies abroad.

“The situation is being resolved professionally, constructively and in the interests of our state,” Kyrylo Budanov, the former intelligence chief who is now the head of the president’s office, said in a statement. “I ask everyone to remain calm.”

“The enemy is closely watching every one of our internal disagreements and is waiting for us to start fighting among ourselves,” he said. “To our enemies, I say this directly: You will not live to see it.”

Mr. Zelensky spent days huddled with senior military leaders from across the ranks and sought to bring Mr. Fedorov back into the fold.

After meeting with the president, Mr. Fedorov said a constructive dialogue to address his concerns had begun. “There will definitely be changes,” he said in a statement.

Since Ukrainians have largely accepted that there can be no elections while the war rages, mass demonstrations have become a pressure release valve and a check on power.

Last year, tens of thousands of Ukrainians staged protests across the country after an effort by Mr. Zelensky to neuter the nation’s anti-corruption agencies. The government quickly changed course in response to the protests.

The demonstrations that followed Mr. Fedorov’s firing exposed long-simmering tensions within the military. The infighting was profoundly dangerous, soldiers said, because it could undermine combat cohesion and worsen the military’s personnel crisis by driving disillusioned troops toward desertion.

General Syrskyi remained largely silent as the controversy swirled, posting only videos of himself meeting with commanders on the front. But on Monday, he published a column in the Militarnyi news outlet to respond to what he called a “mythology about conflicts” and to defend his tenure.

He wrote that he was surprised to learn of any conflict with Mr. Fedorov and apologized if any offense had been taken.

“Ukraine is bigger than Fedorov, Syrskyi and any of us,” he wrote. “Ukraine will stand not because it has irreplaceable people, but because it has an army, institutions and millions of people who do their job. Reducing this war to a confrontation between two people is the greatest service we can do to the enemy.”

Ultimately, Mr. Zelensky concluded that removing the general was the only way to restore unity.

Cassandra Vinograd contributed reporting.