 Tartas was the capital of the namesake viscounty of Tartas, which in turn was held, since 1338, in personal union with the bordering lordship of Albret, owned by the House of Albret, one of the most powerful and influential noble families in the region.The House of Albret had been attached to the English cause in the 14th century, as vassal in Aquitaine under Edward, the Black Prince, but switched sides in the late 1360s and was aligned to the House of Valois ever since.The Lord of Albret at the time of the siege of Tartas was Charles II.