Although much is known about the political stance of the military at large during the Civil War, the political party affiliations of individual soldiers have received little attention. Drawing on archival sources from twenty-five generals and 250 volunteer officers and enlisted men, John Matsui offers the first major study to examine the ways in which individual politics were as important as military considerations to battlefield outcomes and how the experience of war could alter soldiers’ political views. The conservative war aims pursued by Abraham Lincoln and his generals in the first year of the American Civil War focused on the preservation of the Union and the restoration of the antebellum status quo. This approach was particularly evident in the prevailing policies and attitudes toward the Confederacy-supporting Southern civilians and African American slaves. But this changed in Virginia during the summer of 1862 with the formation of the Army of Virginia. If the Army of the Potomac (the major Union force in Virginia) was dominated by generals who concurred with the ideology of the Democratic Party, the Army of Virginia was its political opposite, from its senior generals to the common soldiers. The majority of officers and soldiers in the Army of Virginia saw slavery and pro-Confederate civilians as crucial components of the rebel war effort and blamed them for prolonging the war. Ultimately, the frustrating occupation experiences of the Army of Virginia radicalized them and other Union soldiers against Southern rebellion and slavery, paving the way for Abraham Lincoln to issue the Emancipation Proclamation.