Ukraine war shakeup after Oval Office clash An Oval Office showdown between President Trump and Ukrainian President Volodymyr Zelenskyy would have been cheered by Russian President Vladimir Putin, according to Lt. Gen. H.R. McMaster, who served as Mr. Trump's national security adviser during his first administration. The U.S. imposed sanctions on Russia and provided aid to Ukraine after the war began but last month, Mr. Trump flipped U.S. policy on its head.