The Constitution states that it is Congress that declares war, but it is the presidents who have more often taken us to war and decided how to wage it.
In Waging War, David J. Barron opens with an account of George Washington and the Continental Congress over Washington’s plan to burn New York City before the British invasion. Congress ordered him not to, and he obeyed. Barron takes us through all the wars that followed: 1812, the Mexican War, the Civil War, the Spanish-American war, World Wars One and Two, Korea, Vietnam, Iraq, and now, most spectacularly, the War on Terror.