The garrison's defences were supported with artillery fire from a Royalist warship that was deliberately run aground north of the castle to produce an additional gun platform. By July, food had begun to run short and some of the garrison unsuccessfully attempted to break out by sea to acquire supplies. Arundell agreed to an honourable surrender on 15 August, and around 900 survivors left the fort two days later, some terminally ill from malnutrition. Pendennis was the penultimate Royalist fortification to hold out in the war.