When Lancaster's fleet sailed up the Gironde estuary and disembarked at Bordeaux on 9 August 1345 the duchy of Aquitaine was only a pale shadow of what it had once been. The territories under English control were limited to the southern coastal towns of Bayonne and Bordeaux, Saint-Sever and the maritime strip of land which joined them. There were no towns deeper inland which had remained loyal to Edward III, as French forces had advanced as close as Libourne, to the east/north-east of Bordeaux, and to Langon in the south. The principal aim of the expedition was simply to recapture the key fortifications that had fallen to the French, and to regain control of areas that had been gradually encroached upon since Philippe VI had declared the duchy confiscate in May 1337. The grant of extensive administrative, judicial and military powers to the king's lieutenant suggests, as Jonathan Sumption points out, that ‘his military objectives were left entirely to his own discretion’. It is unlikely that Lancaster had any preconceived plans of attack before landing in Aquitaine, and the openness of his objectives is reflected by the lack of precision in his indenture with the king, which simply states that ‘if there is war … to do the best he can’ (si guerre soit, et a faire le bien q'il poet).

The first acts of warfare in the duchy had begun in the regions surrounding Bordeaux two months prior to the arrival of Lancaster. Local Gascon lords allied to the English conducted raids in Agenais, Périgord and Saintonge, which resulted in the capture of Montravel and several other formidable castles along the Dordogne river. It was in the second half of June, however, that the official offensive began when the English seneschal, Ralph, Lord Stafford laid siege to Blaye.6 This garrison town lies roughly 40 kilometres north of Bordeaux and seems to have been an obvious choice of attack given its proximity to the provincial capital and its strategic position on the north bank of the Gironde. Stafford then doubled back and marched up the Garonne valley and laid siege to Langon, having left part of the Gascon forces behind at Blaye.