In September Henry accompanied his imperial guest to Calais, where they were met by the Duke of Burgundy. A treaty was drawn up by which it was stipulated that the Duke should assist the English king in his proposed conquest of France, and should have in return a share of the spoil. But it was not executed. The Duke shrank from committing himself to a course of action so unprincipled, and indeed so perilous to himself, for his best hope of independence lay in the rivalry between France and England. But though the treaty was not executed, the very fact of the meeting at which it had been discussed did much to serve Henry’s purpose. It increased the dislike and suspicion which the party that was in power in France already entertained for the Duke. Meanwhile hostilities, which there is no need to describe in detail, had been going on. The Earl of Dorset (soon afterwards created Duke of Exeter), who was in command of the garrison at Harfleur, made a plundering expedition into the adjoining country, and found some difficulty in making his way back. In May the French made a retaliatory expedition against the southern shore of England, and ravaged the island of Portland. Later in the year Harfleur itself was besieged, and though it was twice successfully relieved, the fact made it evident that so far France remained unconquered. It is said that Henry was bent on conducting one of these relieving expeditions in person, but was dissuaded by his new friend Sigismund on the ground that the enterprise was not sufficiently important to call for his interference. Whatever the cause, he remained at home, organising his forces, collecting by whatever means were available--some of them, one cannot but think, not altogether creditable--the necessary funds, and generally preparing himself for an effort that should be final and conclusive. Early in 1417 he sent letters under the Privy Seal addressed to the nobles and gentlemen of the country, enjoining their attendance, either in person or by deputy, and making inquiry what number of men they could bring into the field. Further instructions were given a little later in the year to the effect that all persons so serving should attend at court and execute the indentures which should secure them their pay. Special attention was paid to the efficiency of the force of archers, and orders were issued to the sheriffs, enjoining the supply of a certain quantity of goose-quills for the feathering of the arrows.