 Complete the following phrase:  During the Civil War, Fort Walker was a Confederate fort in what is now Port Royal Plantation. The fort was a station for Confederate troops, and its guns helped protect the entrance to Port Royal Sound, which is fed by two slow-moving and navigable rivers, the Broad River and the Beaufort River. It was vital to the Sea Island Cotton trade and the southern economy. On October 29, 1861, the largest fleet ever assembled in North America moved south to seize it. In the 