The secretary of defense is the principal defense policy advisor to the president, under whose direction they exercise authority over the Department of Defense. In National Security Council (NSC) meetings, the secretary analyzes the security situation in the relevant region and explains the likely implications of U.S. military involvement, both for the immediate crisis and for the United States’ overall strategic position.

The secretary of defense’s goals are to

- understand the options for and feasibility of any military action, as well as its possible outcomes; and
- identify ways to prevent the deterioration of a crisis to the point where it mandates U.S. military intervention.