Complex sentence: With both the Austrian Empire and the Kingdom of Prussia to join his opponents, Napoleon withdrew more troops from Spain, including some foreign units and three battalions of sailors sent to assist with the Siege of Cádiz.
Split into simpler sentences: With both the Austrian Empire and the Kingdom of Prussia to join his opponents, Napoleon responded by withdrawing more troops from Spain. Taken were a few more foreign units, together with three battalions of sailors who had been sent to assist with the Siege of Cádiz.