In the subsequent campaigns of the Army of the Potomac, Howe fought in the Battle of South Mountain and was present at the Battle of Antietam. He was promoted to command 2nd Division, VI Corps, leading it at the Battle of Fredericksburg. His division was heavily engaged at Fredericksburg and Salem Church during the Chancellorsville Campaign. Howe's division led a reconnaissance in the vicinity of Fredericksburg on June 3, 1863, as the Union high command tried to determine whether the Army of Northern Virginia was moving out of its positions to undertake an offensive. It was only minimally engaged in the campaign culminating in the Battle of Gettysburg. His division was the last to reach the battlefield and his two brigades were assigned to opposite ends of the Union line, leaving him effectively without a command. During the pursuit of Lee's retreating army, the 1st Vermont Brigade of Howe's division fought the Confederate rear guard near Funkstown, Maryland, on July 10, 1863. Howe continued in division command during the Bristoe Campaign and the Mine Run Campaign.