Complex sentence: At the Battle of Gettysburg, Lane briefly assumed command of Pender's division following that officer's mortal wounding on July 2,1863, but he was replaced by Maj. Gen. Isaac R. Trimble and returned to lead his brigade during Pickett's Charge.
Split into simpler sentences: At the Battle of Gettysburg, Lane's brigade fought on the first day (July 1,1863) and Lane briefly assumed command of Pender's division following that officer's mortal wounding on the second day. He was replaced in division command by Maj. Gen. Isaac R. Trimble and returned to lead his brigade during Pickett's Charge.