By the time Abraham Lincoln was inaugurated in March 1861, seven states had separated from the Union and set up the Confederate States of America. A little over five weeks later, rebel gunners opened fire on Fort Sumter in Charleston harbor. In response, Lincoln called for 75,000 volunteers to serve ninety days. Denouncing the president’s policy of “coercion,” four more states left the Union. The ensuing war, the most costly in American history, would last for four years. When it was over, some 600,000 Americans had died and the South had suffered staggering economic losses.

Entering uncharted waters as he confronted the rebellion, Lincoln claimed broad emergency powers that he argued the Constitution had vested in the executive branch. Although he asserted powers as commander in chief that presidents had not before used, he did not create his war power out of whole cloth. Lincoln found the power he needed to deal with the rebellion in the commander-in-chief clause of the Constitution, in the clause of Section II requiring him to “take care that the laws be faithfully executed,” and in his presidential oath “to preserve, protect, and defend the Constitution of the U.S.”

Based on these powers, he called out the militia, authorized increases in the size of the regular army and navy, expended funds for military purchases, deployed military forces, blockaded Southern ports, suspended the writ of habeas corpus in certain areas, authorized arbitrary arrests, and empanelled military tribunals to try civilians in occupied or contested areas. Later he authorized conscription and issued the Emancipation Proclamation. Lincoln justified these steps as necessary to save the Union and preserve the Constitution.

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https:// ashbrook.org/publications/onprin-feb2009-owens/