Complex sentence: Their ranks severely depleted by death and the expiration of enlistments, North Carolina's ten regiments were reduced to four, and superflous officers, including Polk, were removed by lot from active service.
Split into simpler sentences: Their ranks severely depleted by death and the expiration of enlistments, North Carolina's ten regiments were reduced to four. Superflous officers, including Polk, were removed by lot from active service.