Complex sentence: The assault was successful and the walls were breached, but the commanders supposedly lost control of their soldiers and a massacre of the populace ensued in which 25,000 of the 30,000 inhabitants of the city perished by sword and the fire which destroyed most of the city.
Split into simpler sentences: The assault was successful and the walls were breached, but the commanders supposedly lost control of their soldiers. A massacre of the populace ensued in which 25,000 of the 30,000 inhabitants of the city perished by sword and the fire which destroyed most of the city.