The loss of Volodymyr Zelenskyy's closest aide is a huge personal blow for the Ukrainian president, and could well weaken his authority.
Andrii Yermak resigned on Friday, hours after anti-corruption officials raided his home amid a major corruption scandal that has shaken the country.
Two ministers have already been forced to resign.
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But Yermak is by far the most significant departure from Zelenskyy's inner circle since Russia launched its full-scale invasion almost four years ago.
The dramatic move could not have come at a worse time for Ukraine, which is under daily Russian bombardment as well as increased American pressure to strike a deal with Moscow to end the war.
At a time when he needs to be stronger than ever, Zelenskyy will instead cut a lonely figure without his towering chief of staff, who has been by his side since he ran for president in 2019 and has been a hugely influential confidant ever since the first Russian missiles targeted Kyiv on 24 February 2022.
Yermak, despite being an unelected figure, has wielded tremendous power, including over ministerial and military appointments and over who had access to the president.
He was also appointed lead negotiator in peace talks, most recently representing Ukraine in Geneva alongside the US secretary of state Marco Rubio.
But critics have long been wary about his elevated wartime status, with Yermak effectively the second most powerful person in the country after Zelenskyy.
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It meant questions were immediately raised about what he may or may not have known when it emerged earlier this month that Ukraine's two main anti-corruption agencies had uncovered a plot to control contracts at the state atomic energy agency worth around $100m (£76m) in kickbacks and laundered money.
It is not yet clear what investigators were looking for when they raided Yermak's home, and he has said he was cooperating fully. He has not been charged with any crime or named as a suspect.
However, anti-corruption activists were quick to demand he leave his job or else risk tarnishing Zelenskyy's reputation in the scandal as well.
(c) Sky News 2025: Zelenskyy will cut a lonely figure without his towering chief of staff


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