Parliament defeated the wider insurgency at the Battle of Maidstone at the start of June and then sent a force under the command of Colonel Nathaniel Rich to deal with Deal and the other castles along the Downs.[39] Walmer Castle was the first to be besieged and surrendered on 12 July.[40] Deal, which had been resupplied by the Royalists from the sea, was besieged in July.[41] A Royalist fleet bombarded the Parliamentary positions and temporarily landed a force of 1,500 Flemish mercenaries in support of the revolt, but a shortage of money forced their return to the Continent.[42] The garrison then carried out a surprise attack on their besiegers but were fought back with some losses.[5] The fleet, under the command of Prince Charles, attempted to land a fresh force in August, but despite three attempts the operation failed and suffered heavy losses.[43] After news arrived of the Royalist defeat at Preston, Deal surrendered on 20 August and artillery assaults then began on Sandown, leading to the surrender of the remaining fortification.[44]