The British attack on Lewes, Delaware, during the War of 1812 demonstrated the need for forts to protect the Delaware River and the ports of Wilmington and Philadelphia. The War Department recognized Pea Patch Island's strategic location and built two defensive structures there between 1813 and 1827, the second of which burned in 1831. The present Fort Delaware, completed in 1859, just two years before the Civil War began, was a thoroughly modern defensive structure. Because the weak Confederate navy posed no real threat to the cities along the Delaware and because the Union needed a facility to hold prisoners, the War Department converted the fort into a prisoner of war camp. Beginning in 1862, captured Confederate soldiers, political prisoners and federal convicts were imprisoned on the island. Following the Battle of Gettysburg in July 1863, there were between 11,000 and 12,000 prisoners on Pea Patch Island; over the course of the war, the island held 33,000 prisoners in all. During the Civil War, many structures were erected outside the fortified walls, including officers' and civilians' quarters, a church, commercial buildings, workshops, and wooden barracks for the thousands of Confederate prisoners. A thirty-foot-wide moat surrounds the brick and stone pentagon-shaped fort, whose state-of-the-art armaments and thirty-two-foot-high walls, measuring seven to thirty feet thick, made it formidable. In 1945 the federal government declared the island and the fort surplus, and in 1951 they became state property and the second state park in Delaware. Across the Delaware River, Forts Mott, Delaware, and DuPont formed a three-fort defense system. The War Department began building Fort Mott in the 1870s, and although it was named for Major General Gershom Mott, it was not completed until 1897. On the site later named for Admiral Samuel Francis DuPont, the War Department established a gun battery in 1863; its initial fortifications consisted of a ten-gun auxiliary battery that during the Civil War was called Ten Gun Battery, and most of the fort's buildings were constructed between 1898 and 1901. Fort DuPont served as headquarters for the harbor defense of the Delaware River during World War I and World War II, and it held nearly 3,000 German prisoners of war during World War II. All three forts are now state parks, with Fort Delaware and Fort DuPont under Delaware's Division of Parks and Recreation and Fort Mott under the New Jersey Division of Parks and Forestry.