The flag of the Chairman of the Joint Chiefs of Staff was approved by the Secretary of Defense in 1949. The diagonal division of the field is borrowed from the flag of the Chief of Staff of the Army, while the colors and the central device come from that of the Secretary of Defense. The Chairman is by law the senior officer in the United States military service and the principal military adviser to the President, Congress, and the Secretary of Defense. The Secretary's orders to the operating forces are passed through the Chairman of the Joint Chiefs of Staff, but he has no command authority of his own.