Complex sentence: At the Battle of Balls Bluff, in 1861, he was severely wounded; he was again wounded at the Battle of Fair Oaks in 1862 and at the Battle of Chancellorsville in 1863, where he commanded a division.
Split into simpler sentences: At the Battle of Balls Bluff, in 1861, he was severely wounded. He was again wounded at the Battle of Fair Oaks in 1862 and at the Battle of Chancellorsville in 1863, where he commanded a division.