KYIV, Nov. 29 -- Ask Ukrainians who the country's most powerful figure was after the president, and many would say Andriy Yermak, his chief of staff and a key negotiator during four years of war when Western support has kept Kyiv in the fight. Not any more.

Yermak, a friend of President Volodymyr Zelenskiy and his trusted right-hand man, resigned today after he became ensnared in an evolving corruption scandal when anti-graft agents searched his property.

The 54-year-old is the highest-profile casualty so far of a corruption investigation that has also seen two ministers step down, and his removal from office leaves Zelenskiy looking more isolated than at any time since the full-scale war began.

It comes at a perilous time for Kyiv as ...