President-elect Donald Trump said Thursday that he had chosen retired Marine Gen. James Mattis to be his secretary of defense. Mattis, known as “Mad Dog,” has a reputation for strong, aggressive thinking, and shares Trump’s hardline stance against potential enemies abroad, especially Iran. Mattis, 66, only left the military four years ago, so before he can be confirmed in the job, Congress will need to pass legislation to bypass a law requiring defense secretaries to have been out of uniform for at least seven years. Trump’s transition team and Mattis declined to comment. An official announcement could come as soon as next week.