Complex sentence: In spite of Patton's effectiveness, General Dwight D. Eisenhower, the commander of the Sicily operation and Patton's friend and commanding officer, had long noted Patton's colorful leadership style also meant he was prone to impulsiveness and a lack of self-restraint.
Split into simpler sentences: In spite of Patton's effectiveness, General Dwight D. Eisenhower, the commander of the Sicily operation and Patton's friend and commanding officer, had long noted Patton's colorful leadership style. However, Eisenhower also knew that Patton was prone to impulsiveness and a lack of self-restraint.