washington congress expect approve president-elect donald trump choice retire marine corps general jam mad dog mattis secretary defense despite democratic concern ignore long tradition civilian control military mattis confirm senate house representatives must pass waiver exempt law write department defense create ensure military civilian command.legislators grant waiver 1950 congress pass act allow general george marshall retire 1945 serve pentagon chief 66-year-old mattis revere fellow marines retire 3-1/2 years ago 1947 national security act require seven-year gap active duty military service cabinet position leave chairman joint chiefs staff pentagon top uniform military position another marine general joseph dunford current chairman serve two-year term end mid-2017 mattis dunford commander lawrence korb assistant secretary defense republican president ronald reagan say military officer secretary defense would rob pentagon need perspective note example social change military end segregation allow women combat always push civilians think good idea military person secretary defense say friday telephone interview trump take office jan. 20. trump announce selection thursday democrats join many republicans control majorities house congress heap praise mattis also raise concern many general top tiers government trump choice national security adviser michael flynn retire army lieutenant general former director defense intelligence agency president-elect also say consider david petraeus another retire army general secretary state retire marine general john kelly head department homeland security senator kirsten gillibrand new york democrat arm service committee say thursday would back waiver mattis chris murphy another senate democrat say friday deeply fearful precedent civilian control military could wither although would talk mattis speak highly military leader would really dangerous precedent break tell news conference connecticut home state representative adam smith top democrat house arm service committee high praise mattis say house perform full review include committee hear consider override prohibition recent military officer lead pentagon civil control military something casually cast aside smith say statement mattis likely become defense secretary despite democrats concern