Complex sentence: Each fort was a basic earth and timber structure surrounded by a ditch with a movable drawbridge at the entrance to the fort, and each was furnished with an underground magazine to house two hundred rounds of artillery shells.
Split into simpler sentences: Each fort was a basic earth-and-timber structure surrounded by a ditch with a movable drawbridge at the entrance to the fort. Each was furnished with an underground magazine to house two hundred rounds of artillery shells.