Complex sentence: Boniface of Montferrat received Thessalonica when the Crusaders distributed the Byzantine Empire among themselves in the autumn of 1204, and went on to conquer Thessaly, Boeotia and Attica in November, granting these regions to his commanders.
Split into simpler sentences: Boniface of Montferrat received Thessalonica when the crusaders distributed the Byzantine Empire among themselves in the autumn of 1204. He conquered Thessaly, Boeotia and Attica in November and granted these regions to his commanders.