Complex sentence: The grenadiers of the 1st Regiment then took the manor and set it on fire as well, and then were able to enter the church through the vestry, which they also torched prior to withdrawing under the fire of the Patriotes in the balcony.
Split into simpler sentences: The grenadiers of the 1st Regiment then took the manor and set it on fire as well. They were then able to enter the church through the vestry, which they also torched prior to withdrawing under the fire of the Patriotes in the balcony.