The siege of Tartas (31 August 1440 – 24 June 1442) in Gascony was an engagement between English and French forces in the late stages of the Hundred Years' War.

The conduct of this affair became an important subject as one of the arrangements concluded in 1441 stated that Albret had to switch his allegiance if his suzerain, Charles VII of France, failed to aid him against his enemies.

[4] In 1439, the English sent to the region an army of 2,300 men (2,000 archers and 300 men-at-arms) under the command of John Holland, Earl of Huntingdon,[5] appointed lieutenant of Aquitaine on 27 March.

[6][7] Holland landed with his force at Bordeaux on 2 August 1439, and was shortly afterwards joined by sir Thomas Rempston[8] (the English seneschal of Guyenne)[9] and by other important English-attached figures in the region.

[1] Anticipating an Anglo-Gascon onslaught, in October 1439 the French Estates of Languedoc in southern France assembled at Castres and raised a subsidy to defend Guyenne and Gascony against Holland's army.

Charles II of Albret and his nephew John, Viscount of Lomagne (eldest son and heir of John IV, Count of Armagnac, another powerful nobleman in the region), attempted to raise the siege by ravaging nearby English lands, in particular the Chalosse and the lands of the Lord of Lescun (Rempston's lieutenant), which in turn included Coudures, Audignon, Sainte-Colombe, and Eyres.

As a guarantee to enforce the terms, the Lord of Albret handed Tartas over to Charles, his underage son, who would be placed under the tutelage of several prominent Gascon figures who were attached to the English.

The most important point agreed, however, was one that stipulated that a trial of strength would be held at Tartas between the French and the English on the day the truce ended, and that the strongest side left standing would be awarded control of the town.

[1] Albret had essentially agreed that if his overlord, Charles VII of France, failed to come to his aid, he would switch his allegiance, thus placing all of his lands under the suzerainty of the English.

Though it could be thought that a small Gascon town would not have concerned the king much in normal circumstances, the consequences of a potential defection from one of his most powerful vassals in Gascony would be disastrous for the Valois regime in southwestern France.

Southwestern France was home to several influential nobles, such as the Counts of Armagnac, Foix, and Comminges, whose support would determine the balance of power in the region.

Though the Gascon Estates sent emissaries to England in February 1441 to update King Henry VI on the situation and to request aid, little to no help was forthcoming for the time being.

He led a difficult campaign against the English in the Île-de-France in 1441, and in early 1442, he had a meeting at Nevers with his some of his leading nobles, who made various requests not too dissimilar to those which formed the pretext of the Praguerie revolt two years earlier.

Among these nobles were the Dukes of Orléans and Burgundy, whose families had previously been mortal enemies in the Armagnac–Burgundian Civil War several decades earlier, but were now close political allies.

[17] Charles VII assembled a large army, essentially provided by smaller nobility, as his leading vassals and princes of blood, the dukes of Orléans, Burgundy, Alençon, and Bourbon, who were all at odds with their overlord, did not bother contributing to the force.

The French captain La Hire arrived the following day, after, according to legend, having fought a group of English routiers and assaulted a castle close to Ygos.

On 23 June, Charles VII stayed in the fortified town of Meilhan (which belonged to the Count of Foix), and in the following day he went to Tartas along the Midouze river.

Perhaps fearful of losing his lands, the Lord of Cauna afterwards paid homage to Charles VII, but Saint-Per remained faithful to the English party and took refuge in nearby Dax.

After taking La Réole on 8 December[20] (where Charles VII was almost burnt within a house which was set on fire),[21] the French withdrew to Montauban on 23 of the same month to spend the winter, marking the end of the campaign.

Henry VI received a letter from his secretary Thomas Beckington, dated on 18 October 1442, which informed the king about the enemy's progress in Guyenne and the capture of La Réole.

It also complained about the lack of support from the English crown in the situation, stating that a few reinforcements would have stopped the French advance and even resulted in the possible capture of Charles VII himself.

It is not totally clear whether the English crown couldn't send men or if the lack of action was the result of neglect from Henry VI's ministers.