Complex sentence: While the rest of Longstreet's corps was located around Suffolk, Virginia, Alexander accompanied Stonewall Jackson on his flanking march at the Battle of Chancellorsville in May 1863, and his artillery placements in Hazel Grove at the Battle of Chancellorsville proved decisive.
Split into simpler sentences: While the rest of Longstreet's corps was located around Suffolk, Virginia, Alexander accompanied Stonewall Jackson on his flanking march at the Battle of Chancellorsville in May 1863. And his artillery placements in Hazel Grove at the Battle of Chancellorsville proved decisive.