Complex sentence: During the assault of the three regiments, the 11th New York noticed that General J. E. B. Stuart Stuart was flanking, the 11th changed fronts and repulsed the cavalry assault.
Split into simpler sentences: During the assault of the three regiments, the 11th New York noticed that General J. E. B. Stuart Stuart was flanking. The 11th changed fronts and repulsed the cavalry assault.