In 1642 the English Civil War broke out between the Royalist supporters of Charles I and those of Parliament. South Wales was predominantly Royalist in sympathy, and during the conflict, a sconce, or small fort, was built overlooking Caerphilly Castle to the north-west, on the site of the old Roman fort. It is uncertain if this was built by Royalist forces or by the Parliamentary army that occupied the area during the final months of the war in March 1646, but the fort's guns would have dominated the interior of the castle. It is also uncertain whether or not Caerphilly Castle was deliberately slighted by Parliament to prevent its future use as a fortification. Although several towers had collapsed by the 18th century, possibly as a result of such an operation, it is probable that this deterioration was actually the result of subsidence damage caused when the water defences retreated, as there is no evidence of deliberate destruction having been ordered.