Complex sentence: The Italian commander General Roatta planned that his forces would surround the defences of Madrid from the Northwest, and after joining on Jarama River with the Spanish Nationalist corps "Madrid", they would begin the assault on Madrid.
Split into simpler sentences: The Italian commander General Roatta planned that his forces would surround the defences of Madrid from the north-west. After joining the Spanish Nationalist corps "Madrid" on Jarama River, they would begin the assault on Madrid.