Civilian control of the Armed Forces has been a bedrock principle of American government since our Revolution. A painting hanging in the Capitol Rotunda celebrates the legacy of George Washington, who voluntarily resigned his commission as Commander of the Continental Army to the Congress. This principle is enshrined in our Constitution, which divides control of the Armed Forces among the President, as Commander in Chief, and the Congress as coequal branches of government. Since then, Congress has adopted various provisions separating military and civilian positions. In the 19th century, for example, Congress prohibited an Army officer from accepting a civil office. More recently, in the National Security Act of 1947 and subsequent revisions, Congress has prohibited any individual from serving as Secretary of Defense within seven years of Active Duty service as a commissioned officer in the Armed Forces. It was only three years later, in 1950, that Congress granted General George Marshall an exemption to that law and the Senate confirmed him to be Secretary of Defense. Indeed, the separation between civilian and military positions has not always been so clear. Twelve of our Nation's Presidents previously served as generals in the Armed Forces. Over the years, numerous high-ranking civilian officials in the Department of Defense have had long careers in military service. The basic responsibilities of civilian and military leaders are simple enough: for civilian leaders, to seek the best professional military advice while under no obligation to follow it; for military leaders, to provide candid counsel while recognizing civilians have the final say or, as James Mattis once observed, to insist on being heard and never insist on being obeyed. Ultimately, the key to healthy civil-military relations and civilian control of the military is the oath soldiers and statesmen share in common, to protect and defend the Constitution.