As of 1836, the main defensive position in the Line Wall was the King's Bastion, at the centre of the harbour. This was built by General Sir Robert Boyd in 1772 on the site of an old Moorish gate that had been replaced by a Spanish bastion. It played a key role in the defence of Gibraltar during its Great Siege (1779–1783), providing the platform from which red hot shot was fired at the floating batteries of the Spanish forces. At that time, the main sea defenses consisted on the North, Montagu, Orange, King's and South bastions, with the line wall curtain connecting these positions.