President-elect Donald Trump has chosen retired Marine Gen. James Mattis to be his secretary of defense, he confirmed during a rally Thursday in Ohio. Mattis is respected in the field and has a reputation for strong, aggressive thinking, and like Trump favors a more adversarial stance against potential enemies abroad. Mattis retired in early 2013 after serving for more than four decades; because he left active military service less than seven years ago, Congress will need to grant Mattis an exception to a federal law that requires defense secretaries be more than seven years removed from active duty. Trump said an official announcement will be made on Monday.