Swansea Port was graded as a Class C commercial harbour by the Home Ports Defence Committee, later the Home Defence Committee with the defences designed to resist attack from unarmoured cruisers and block ships. There were no coastal defence fortifications built within Swansea itself.
The Mumbles Battery (Mumbles Island Battery) was initially a casemated battery with two guns inside a tower. By 1882 the Battery was armed with five 80-pdr guns. Between 1899 and 1901 two 4.7-inch Q.F. guns were mounted on the roof of the tower and the old casemated battery sealed off and filled with debris to increase its’ protection. The Mumbles Battery was the primary coastal defence for the Port of Swansea.