Gibraltar is a promontory surrounded by water except for the isthmus connected to Spain. This vulnerability to a land attack prompted the Kingdom of Castile to build the Giralda Tower in 1309 immediately after defeating the Moors. When the Moors regained control in 1333, they enhanced the tower and wall along the harbor. In 1462, the Spanish ousted the Moors for the last time. About a century later, Philip II of Spain determined the northern defenses were totally inadequate. The king ordered the construction of an enormous curtainwall. It was named Baluarte San Pablo meaning St. Paul’s Bastion. When the British seized Gibraltar in the early 18th century, they spent years expanding the fortification. They also armed it with 13 cannons pointing out of the embrasures toward the sea, harbor and land. North Bastion was critical during the British victory over Spain during the Siege of Gibraltar of 1727.