Through 1416 the war was limited to a contest for the command of the Channel, till the increasing bitterness of the strife between the Burgundians and Armagnacs, and the consent of John of Burgundy to conclude an alliance, encouraged Henry to resume his attempt to recover Normandy.

Whatever may have been his aim in this enterprise--whether it were, as has been suggested, to provide a refuge for his house, should its power be broken in England, or simply to acquire a command of the seas--the patience and skill with which his object was accomplished raise him high in the rank of military leaders.

Disembarking in July 1417 with an army of forty thousand men near the mouth of the Touque, he stormed Caen, received the surrender of Bayeux, reduced Alencon and Falaise, and detaching his brother the Duke of Gloucester in the spring of 1418 to occupy the Cotentin made himself master of Avranches and Domfront.

With Lower Normandy wholly in his hands, he advanced upon Evreux, captured Louviers, and seizing Pont-de-l'Arche, threw his troops across the Seine.
The end of these masterly movements was now revealed.

Rouen was at this time the largest and wealthiest of the towns of France; its walls were defended by a powerful artillery; Alan Blanchard, a brave and resolute patriot, infused the fire of his own temper into the vast population; and the garrison, already strong, was backed by fifteen thousand citizens in arms.