the son and heir of Philip VI, gathered an army reportedly numbering over 20,000 and manoeuvred in the area. In early October a very large detachment relieved the city, drove off Grosmont's force and started besieging the English-held strongpoints. A French force of 7,000 besieged the castle of Auberoche, east of Périgueux. A messenger got through to Grosmont, who was already returning to the area with a scratch force of 1,200 English and Gascon soldiers: 400 men-at-arms and 800 mounted archers. After a night march Grosmont attacked the French camp on 21 October while they were at dinner, taking the French by surprise. There was a protracted hand-to-hand struggle, which ended when the commander of the small English garrison in the castle sortied and fell upon the rear of the French. They broke and fled. Derby's mounted men-at-arms pursued them relentlessly. French casualties are uncertain but heavy. They are described by modern historians as "appalling", "extremely high", "staggering", and "heavy". Many French nobles were taken prisoner; lower ranking men were, as was customary, put to the sword. The ransoms alone made a fortune for many of the soldiers in Grosmont's army, as well as Grosmont himself, who was said to have made at least £50,000 from the day's captives. The Earl of Pembroke arrived after hostilities had ceased; Grosmont greeted him with the words, "cousin Pembroke, welcome. You are just in time to sprinkle holy water upon the dead." Grosmont's four-month campaign has been described as "the first successful land campaign of... the Hundred Years' War", which had commenced more than eight years earlier. Modern historians have praised the generalship demonstrated by Grosmont in this campaign: "superb and innovative tactician"; "ris[ing] to the level of genius"; "brilliant in the extreme"; "stunning"; "brilliant". 1346 The Duke of Normandy was placed in charge of all French forces in southwest France in 1346, as he had been the previous autumn. In March 1346 a French army under Duke John, numbering between 15,000 and 20,000, enormously superior to any force the Anglo-Gascons could field, marched on the town of Aiguillon and besieged it on 1April. The town commanded the junction of the Rivers Garonne and Lot, meaning it was not possible for the French to sustain an offensive further into Gascony unless the town was taken. On 2April an arrière-ban, a formal call to arms for all able-bodied males, was announced for southern France.