Philip of France, obeying the exhortation of the Pope to assist in dethroning John, had made extensive preparations for the invasion of England, and when in 1213 John became the Pope's vassal Philip did not like the idea of giving up the project. John, therefore, found it necessary to adopt retaliatory measures. All men capable of bearing arms were ordered to assemble at Dover "for the defence of the king's and their own heads, and the land of England," and the bailiffs of all the ports were forbidden to suffer any ship to sail without the king's express authority. The French king entered Flanders to punish the count, who had refused to join the expedition against John, and despatched all the ships which he had collected to the port of Damme, the harbour of which, though of "wonderful size," could not contain all the French ships, which are said to have numbered one thousand seven hundred sail. Thither the English fleet, of five hundred sail the greater portion consisting of ships from the Cinque Ports, under William Longsword, proceeded at the urgent summons of the count. On the arrival of the English they found that the French had landed and were ravaging the surrounding country, whereupon they attacked the fleet in the harbour, and three hundred vessels laden with corn, wine, and arms, fell into English hands. The cables of the captured vessels were cut, and the wind being off the land, they were soon on the passage to England. About a hundred others were burnt, and the first great naval victory recorded in English annals was complete. The attitude of the Cinque Ports during the period immediately preceding the granting of the Great Charter of English Liberties is obscure. They are mentioned as guaranteed in their franchises when the Charter took its final shape under Henry III., and it is clear that, when the baronage invited Louis of France to depose the faithless King of England, the ports resolved to stand by the House of Plantagenet. John's unexpected death in 1216, at a time when London and a great part of Kent were in the power of Louis, found the Cinque Ports--though Sandwich had been burnt by the French--staunch to the loyal Earl of Pembroke--marshal of the kingdom, and supporters of the boy-king, Henry III.