The siege of Saint-Denis (Late August – 4 October 1435) was the last instance of cooperation between the English and their Burgundian allies in the Hundred Years' War. Saint-Denis, the traditional burial place of the kings of France, was located in the outskirts of English-held Paris, and had been captured by the French a couple of months earlier. The enemy presence there critically endangered the English position in the capital, and, aiming to retake it urgently, the English moved onto the town in August with a handful of Burgundian auxiliaries. The siege was undertaken during the peace congress of Arras, during which no end to the fighting was seen, as both sides struggled to gain ground around and over Paris. The English were victorious at St. Denis after the French garrison surrendered due to lack of external support.
On 21 September 1435, halfway through the siege, the Duke of Burgundy concluded the treaty of Arras with Charles VII of France. The agreement definitely severed the alliance between England and Burgundy. The Burgundians who were fighting alongside the English at Saint-Denis stayed until the end of the siege.
The English did not control Saint-Denis for long. By the time the town had been recovered, the French had taken Meulan, which blocked the main supply route from Paris to Normandy, further isolating the English forces in the French capital. The loss of the alliance with Burgundy crippled the English cause militarily, and following the reconciliation between the Armagnacs and Burgundians, military successes by a now-unified and strengthened French party led to the French capture of Saint-Denis in February 1436, followed by their recapture of Paris on 17 April 1436, further demonstrating their resurgence, and the English decline, in the conflict.
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