Complex sentence: A banquette is a small foot path or elevated step along the inside of a rampart or parapet of a fortification, by which musketeers were able to view the counterscarp, or fire on enemies in the moat.
Split into simpler sentences: A banquette is a small foot path or elevated step along the inside of a rampart or parapet of a fortification. Musketeers atop it were able to view the counterscarp, or fire on enemies in the moat.