Complex sentence: A detachment of the London trainbands sent against him under the command of the Duke of Norfolk also joined the rebels, raising their numbers to 4,000, and the Duke was forced to return to London.
Split into simpler sentences: A detachment of the London trainbands sent against him under the command of the Duke of Norfolk. His force also joined the rebels, raising their numbers to 4,000, and he was forced to return to London.