Complex sentence: On May 16,1863, as a part of General Carr's Fourteenth Division, the regiment remained in reserve until near the end of the battle when they were ordered to pursue the retreating Confederate army.
Split into simpler sentences: On May 16,1863, as a part of General Carr's Fourteenth Division, the regiment remained in reserve until near the end of the battle. At that point, they were ordered to pursue the retreating Confederate army.