Complex sentence: The first victory came at Tippermuir, on 1 September 1644, the next, at Aberdeen, on 13 September 1644, was more controversial in that the Royalists, including O'Cahan's men were involved in the massacre of hundreds of unarmed civilians throughout the city.
Split into simpler sentences: The first victory came at Tippermuir, on 1 September 1644. The next, at Aberdeen, on 13 September 1644, was more controversial in that the Royalists, including O'Cahan's men, were involved in the massacre of hundreds of unarmed civilians throughout the city.