President Trump has instructed his new National Security Adviser to make substantial staffing cuts to the 300-member National Security Council, according to reports — after years of Republican complaints of agency bloat and overreach. Two administration sources told Bloomberg News the order was timed to the arrival of National Security Adviser Robert O’Brien, who took over Sept. 18 from the ousted John Bolton. But the move comes as the administration grapples with an impeachment investigation centered on NSC activity — an inquiry touched off by a whistleblower who is rumored to have worked on the NSC’s Ukraine desk during the...