He preserved the Union, abolished slavery, strengthened the federal government, and modernized the U.S. economy. On foreign and military policy, Lincoln spoke against the Mexican–American War, which he imputed to President James K. Polk's desire for 'military glory—that attractive rainbow, that rises in showers of blood.' He supported the Wilmot Proviso, a failed proposal to ban slavery in any U.S. territory won from Mexico. Historians have said he was 'a classical liberal' in the 19th-century sense. Allen C. Guelzo states that Lincoln was a 'classical liberal democrat—an enemy of artificial hierarchy, a friend to trade and business as ennobling and enabling, and an American counterpart to Mill, Cobden, and Bright' (whose portrait Lincoln hung in his White House office).