President Volodymyr Zelensky has announced the dismissal of Ukraine’s top commander, General Valerii Zaluzhnyi, in the biggest military shakeup since the start of Russia’s full-scale invasion almost two years ago.

The president’s move follows tensions between Zelensky and his hugely popular military chief after the failure of Ukraine’s much-vaunted counteroffensive, and with Ukraine facing a renewed Russian onslaught, manpower and ammunition shortages, and US aid stalled in Congress.

In a Telegram post sent shortly before the formal announcement, Zelensky said he held a meeting with Zaluzhnyi, and “discussed what kind of renewal the Armed Forces of Ukraine need.”

“The time for such a renewal is now,” Zelensky wrote.

Zaluzhnyi’s replacement will be Oleksandr Syrskyi, who since 2019 has served as the Commander of Ukrainian Land Forces.

Zaluzhnyi wrote on his Telegram channel on Thursday that “the tasks of 2022 are different from those of 2024.

“Therefore, everyone must change and adapt to the new realities as well. [We] have just met with the Supreme Commander-in-Chief. It was an important and serious conversation. It was decided that we need to change our approaches and strategy.”

Differences between the two men had been simmering for many months but appeared to grow wider towards the end of last year, after Zaluzhnyi said the war had reached a stalemate in a long essay and interview in The Economist magazine in November.

Writing after Ukraine’s counteroffensive was mostly rebuffed by heavily fortified Russian defenses, he warned that a great technological leap forward “there will most likely be no deep and beautiful breakthrough,” but instead an equilibrium of devastating losses and destruction.

His remarks drew immediate criticism from Zelensky’s office, which said such commentary about the war only benefitted Russia.