Upton Battery was built at about the same time as the new breakwaters were being built on the east side of Portland Harbour. The land was acquired by 1900. The Battery was built between 1901 and September 1903 at a cost of £20,612. The Battery was armed with two 6-inch Mark VII BL guns and two 9.2-inch BL Mark X guns. The guns were to be placed in pairs with shared magazines between the two gun pits. It would appear that the two 6-inch BL guns were not mounted until 1940.
The two 9.2-inch guns were mounted on the east of the battery and the two 6-inch Mark VII guns on the west side. There were two defence electric lights and a position finding station. The position finding station and adjacent blockhouse have been destroyed.