Donald Trump has officially chosen Gen. James Mattis for defense secretary

Donald Trump on Thursday announced retired Marine Corps Gen. James Mattis as his pick for secretary of defense, tasking the popular military leader with carrying out the president-elect's planned overhaul of Pentagon operations and a shift in national security priorities.  Speaking at a rally Thursday night in Cincinnati, Trump confirmed media reports published earlier in the day indicating the president-elect intended to nominate Mattis for the key Cabinet post.   Neither Mattis nor Trump's transition team responded t…