the advice of Bertrand du Guesclin, appointed Constable of France in November 1370, the French adopted an attritional strategy. Rather than seeking battle, the English were worn down by an incremental approach whereby the areas ceded at Bretigny were retaken piece by piece, including Poitiers in 1372. In August 1372, the English suffered a disastrous naval defeat at La Rochelle, when a supply convoy carrying reinforcements for Aquitaine, along with £20,000 to pay the troops, was intercepted and sunk by a Castilian fleet. This exposed the English coast to French and Spanish raids, isolated Gascony and increased public opposition to the war. In addition, Jean III de Grailly, Captal de Buch, a Gascon fighting for the English who had filled the gap left by Chandos, was captured in the fighting around La Rochelle. Despite pleas from his own knights, Charles refused to ransom the Captal, arguing he was too dangerous to release, and kept him in prison where he died in 1376. The English responded with a series of destructive military expeditions into French territory called chevauchées, hoping to bring du Guesclin to battle. The most significant was led by John of Gaunt in 1373; launched between two bouts of the Black Death in 1369 and 1375, the plague had a devastating economic impact, making it difficult for to fund the campaign. According to chronicler Jean Froissart, the Chevauchée had been planned for three years. Known for their capability in this type of warfare, the English plan involved marching from Calais, through Champagne and Burgundy into Aquitaine, a journey of over 1,000 miles, lasting five months. By burning manors, mills and villages, they hoped to destroy the French tax base and demonstrate the inability of Charles to protect his subjects, moving at speed to allow them strike and withdraw before the enemy could respond. On this occasion, Charles issued strict instructions to avoid major combat and ordered farmers to take refuge in fortified towns. As they entered Burgundy, the English columns were tracked by one of du Guesclin's most effective subordinates, Olivier de Clisson, who killed over 600 and took many others prisoner. Most of their baggage and transport was lost crossing the Loire and Allier in October, leaving them short of supplies. By the time they reached Bordeaux on Christmas Eve 1373, the English had been decimated by disease and starvation, with many of the knights on foot. Defeat