New Delhi, Jan. 3 -- President Volodymyr Zelenskyy has chosen Gen. Kyrylo Budanov, Ukraine's head of military intelligence, as his new chief of staff, a move that comes at an especially critical moment in Russia's nearly 4-year-old invasion.

Budanov replaces Andrii Yermak, Zelenskyy's longtime right-hand man who resigned in November after anti-corruption officials raided his apartment in an investigation into alleged graft in Ukraine's energy sector. The move against the powerful aide was a blow to the president that risked disrupting his negotiating strategy amid a U.S. peace effort.

What to know about Budanov:

Rising through the ranks

Budanov has led the military intelligence agency, known by its acronym GUR, since 2020. At 39, he i...