The battery was originally built during the period of Spanish rule over Gibraltar and was known as "Batería de San Joaquín". It was renamed, as was the adjoining plateau, after a British artillery officer called Willis who distinguished himself during the 1704 Capture of Gibraltar. The battery was the first British battery on Willis' Plateau, mounting two guns, and saw active service during the Thirteenth Siege of Gibraltar in 1727. Although it was above sea level, it proved vulnerable to Spanish bombardment and its guns were dismounted by enemy fire. They were positioned very close to the cliff edge with little protection other than a thin wall to prevent their carriages from rolling over the precipice.