11,000–16,000 men[1] The Battle of Saint-Omer, fought on 26 July 1340, was a major engagement in the early stages of the Hundred Years' War, during Edward III's 1340 summer campaign against France launched from Flanders.

The allies suffered heavy losses and the French captured their camp intact, taking many warhorses, draft animals and carts, all the tents, huge quantities of supplies and most of the Flemish standards.

On the bright side, the loss of several thousand men was bearable, as the survivors, which included most of the precious English longbowmen, eventually rejoined him at Tournai.

It exposed southern Flanders to the wrath of Philip VI and enabled the French to concentrate their forces against the main army of the coalition in the siege of Tournai.

[4] By 1340, Flanders had reluctantly been under French suzerainty for centuries[citation needed] and frequent uprisings and wars of independence between the two nations had studded the Middle Ages.

Artevelde agreed, but was secretly unwilling to commit all his resources to this war and also was not fully in control of the mercantile city states which emerged in the semi-independent region.

In addition, Eudes IV, Duke of Burgundy, in his capacity as ruler of Artois maintained garrisons of his own in the western and coastal sector of the frontier[2] The French had not expected an attack on Saint-Omer but the lumbering progress of Edward III's preparations gave them plenty of warning of what was afoot.

Across the front of the army and along its left flank, Robert had constructed lines of ditches and outworks defended by anti-cavalry obstacles carefully camouflaged.

This plan came to nothing when a number of French knights, eager to engage with the enemy and disdainful of orders from their commanders urging restraint charged from the town and into the defended outworks of the allied left wing and were repulsed.

[4] Having failed to capture the town or defeat the French force in open battle, he knew there was no choice but to abandon the campaign before Philip's superior army cut him off from Flanders.

[4] There still were some significant effects; morale amongst the Flemish contingents of Edward's army collapsed, denting the prestige of the coalition and undermining its cohesion.

Within a few days of the battle, representatives of the towns which had suffered especially badly such as Ypres, Bruges and van Artevelde's enemies in Ghent made peace overtures towards Philip, undermining English support in the region.