text: Lee's forces crossed the Potomac River into Maryland, leading to the Battle of Antietam.That battle, a Union victory, was among the bloodiest in American history; it facilitated Lincoln's Emancipation Proclamation in January.McClellan then resisted the president's demand that he pursue Lee's withdrawing army, while General Don Carlos Buell likewise refused orders to move the Army of the Ohio against rebel forces in eastern Tennessee.Lincoln replaced Buell with William Rosecrans; and after the 1862 midterm elections he replaced McClellan with Ambrose Burnside.The appointments were both politically neutral and adroit on Lincoln's part.Burnside, against presidential advice, launched an offensive across the Rappahannock River and was defeated by Lee at Fredericksburg in December.Desertions during 1863 came in the thousands and only increased after Fredericksburg, so Lincoln replaced Burnside with Joseph Hooker.In the 1862 midterm elections the Republicans suffered severe losses due to rising inflation, high taxes, rumors of corruption, suspension of habeas corpus, military draft law, and fears that freed slaves would come North and undermine the labor market.The Emancipation Proclamation gained votes for Republicans in rural New England and the upper Midwest, but cost votes in the Irish and German strongholds and in the lower Midwest, where many Southerners had lived for generations.In the spring of 1863 Lincoln was sufficiently optimistic about upcoming military campaigns to think the end of the war could be near; the plans included attacks by Hooker on Lee north of Richmond, Rosecrans on Chattanooga, Grant on Vicksburg, and a naval assault on Charleston.Hooker was routed by Lee at the Battle of Chancellorsville in May, then resigned and was replaced by George Meade.Meade followed Lee north into Pennsylvania and beat him in the Gettysburg Campaign, but then failed to follow up despite Lincoln's demands.