On the outbreak of the American Civil War Howe served with the Union Army. He fought at Antietam before being badly wounded at Gettysburg. Promoted to the rank of major general, he recovered to take part in the Wilderness campaign.
Hancock was active in politics and in 1880 he was selected by the Democratic Party as its presidential candidate. After losing the election to the Republican candidate, James A. Garfield, he returned to military life. Winfield Scott Hancock died in 1886.