Presidents often exercise enormous power through little more than the stroke of a pen. Harry Truman issued an executive order authorizing his Secretary of Commerce to seize and operate most of the nation's privately-owned steel mills, while Abraham Lincoln suspended Habeas Corpus in a letter to one of his generals and instituted a blockade of southern ports with a presidential proclamation. The constitutional arguments in each instance are similar, and they bring up a fundamental question that we will continue to explore in the next few episodes: what powers do presidents have simply by virtue of being commander-in-chief and chief executive of a sovereign nation?