logistically important town of Aiguillon, "the key to the Gascon plain", on 1 April. On 2 April the arrière-ban, the formal call to arms for all able-bodied males, was announced for the south of France. French financial, logistical and manpower efforts were focused on this offensive. Meanwhile, Edward was raising a fresh army, and assembled more than 700 vessels to transport it – the largest English fleet ever to that date. The French were aware of Edward's efforts, but given the extreme difficulty of disembarking an army other than at a port, and the existence of friendly ports in Brittany and Gascony, the French assumed that Edward would sail for one of the latter – probably Gascony – to relieve Aiguillon. To guard against any possibility of an English landing in northern France, Philip relied on his powerful navy. This reliance was misplaced given the difficulty naval forces of the time had in effectively interdicting opposing fleets, and the French were unable to prevent Edward successfully crossing the Channel. Prelude The campaign began on 11 July 1346, when Edward's fleet departed the south of England. The fleet landed the next day at Saint-Vaast-la-Hougue, from Cherbourg. The English army is estimated by modern historians to have been some 15,000 strong and consisted of both English and Welsh soldiers combined with a number of German and Breton mercenaries and allies. It included at least one Norman baron who was unhappy with the rule of Philip VI. The English achieved complete strategic surprise and marched south. Edward's aim was to conduct a chevauchée, a large-scale raid, across French territory to reduce his opponent's morale and wealth. His soldiers razed every town in their path and looted whatever they could from the populace. The towns of Carentan, Saint-Lô and Torteval were destroyed as the army passed, along with many other smaller places. The English fleet paralleled the army's route, devastating the country for up to inland and taking vast amounts of loot; many ships deserted, having filled their holds. They also captured or burnt over 100 French ships, 61 of which had been converted into military vessels. Caen, the cultural, political, religious and financial centre of north-west Normandy, was stormed on 26 July and subsequently looted for five days. The English marched out towards the River Seine on 1 August. The French military position was difficult. Their main army was committed to the intractable