Complex sentence: The entire province of Moray was soon in revolt against King Edward I's men, and before long Moray had secured Moray, leaving him free to turn his attention to the rest of the northeast of Scotland.
Split into simpler sentences: The entire province of Moray was soon in revolt against King Edward's men, and before long Moray had taken control of it. Once he had secured Moray, he was free to turn his attention to the rest of the northeast of Scotland.