President Volodymyr Zelenskiy has replaced Ukraine's popular army chief with his ground forces commander, a huge gamble at a time when Russian forces are gaining the upper hand nearly two years into their war.
The shake-up ushering in a new military leadership follows months of speculation about a rift between Zelenskiy and army chief General Valeriy Zaluzhnyi, who many Ukrainians see as a national hero.
"As of today, a new management team takes over the leadership of the Armed Forces of Ukraine," Zelenskiy said in a statement on Thursday.
He promoted ground forces chief Colonel General Oleksandr Syrskyi, 58, to be the new head of the Armed Forces, citing his role in overseeing the defence of Kyiv in 2022 and the lightning Kharkiv counteroffensive later that year.
Syrskyi, who goes by the call sign "snow leopard", takes the helm amid deep uncertainty as Kyiv awaits vital military aid from the United States that has been delayed by Republicans in the US Congress for months.
The US State Department said the move to replace Zaluzhnyi was a "sovereign decision", while senior Pentagon official Celeste Wallander said the US would work effectively with his replacement.
With Ukraine struggling to overhaul how it mobilises civilians into the army, the sacking of Zaluzhnyi could deal a blow to troop morale on a 1000km front.
It could also backfire politically, hurting Zelenskiy's ratings.
Zelenskyi said he was grateful to Zaluzhnyi for his time as army chief and posted a photograph of the two men shaking hands and smiling, with Zaluzhnyi flashing the peace sign.
Messages of gratitude for Zaluzhnyi, known widely as the "Iron General", flooded social media following the announcement.
Late last year a poll put the public's trust in Zaluzhnyi at more than 90 per cent - significantly higher than Zelenskiy's 77 per cent.
Under Zaluzhnyi's command, Ukrainian forces rebuffed Russia's initial assault on Kyiv and reclaimed swathes of territory in 2022.
But the battlefield momentum turned against Ukraine last year as a much-vaunted counteroffensive proved unable to break through heavily defended Russian lines.
Russia has since ramped up offensive pressure on the eastern front, trying to cut off and encircle the town of Avdiivka.
Zelenskiy indicated it was last year's setback that underpinned his decision to replace Zaluzhnyi.
"In the second year of this war, we won the Black Sea. We won the winter. We proved that we can regain control over the Ukrainian sky. But, unfortunately, we could not achieve the goals of our state on the ground."
The military shake-up unfolded over a series of statements in which Zelenskiy said he had met Zaluzhnyi to discuss changes to the military leadership, adding that he had asked the general to remain "on his team".
In a separate statement, Zaluzhnyi said he had met Zelenskyi for an "important and serious conversation" and that a decision had been made to change battlefield tactics and strategy.
"The tasks of 2022 are different from the tasks of 2024. Therefore, everyone must change and adapt to new realities as well. To win together too," his statement said.
As ground commander, the new army chief Syrskyi is also closely associated both with Ukraine's initial successes and its more recent setbacks.
In an interview with Reuters last month, he signalled the importance of rotating out exhausted troops who have been under near-constant artillery fire.
"Our task and...one of the reasons for the attention on mobilisation is the timely replenishment of those units that are head for replacement."
