Biggest shake-up of Ukraine’s defense establishment since Russia launched its full-scale invasion in February 2022 KYIV: Ukrainian Defense Minister Oleksii Reznikov submitted his resignation letter to the chairman of parliament, he said in a post on X on Monday. Zelensky said on Sunday he had decided to replace his wartime defense minister, the biggest shake-up of Ukraine’s defense establishment since Russia launched its full-scale invasion in February 2022.