The Battle of Courtrai, or the Battle of the Golden Spurs, pitted Belgium's Flemish peasants against an army of French knights on July 11, 1302.
It is celebrated—July 11th is a national holiday for the Flemish in Belgium—not only because it preserved Flemish independence from France but because it was one of the earliest uprisings of the people against a lord—the king of France—since the fall of Rome.
The peasants, 9,000 strong, were not fighting at the command or provocation of a nobleman leading them. The Count of Flanders, Guy of Dampierre, was at the time in captivity in France.
In fact, the count's relatives did not join in until victory seemed within the Flemish soldiers' grasp. It was the Flemish people themselves who stood up to the French aggressor.
The independence aspect is also important. This battle may be the main reason Dutch is still spoken in Belgium more than seven centuries later. The battle was part of Flanders's efforts to resist the French annexation that had begun two years before.
The Battle
After an exchange of arrows that did little damage to either side, the French tried a 14th-century version of a pincers movement.
The left flank under Raoul de Nesle advanced first. While the story that the defeat is due to the French cavalry running over their own infantry has no basis in fact, the knights were brought up short by the 10-foot-wide Groeninge Brook. Crossing the brook slowed them down and robbed them of their momentum—they had to get back in formation on the other side before they could charge, at which point they were too close to the Flemish lines to gain any sort of speed.
The better-organized right flank got over the brook more easily, and were almost able to break the Flemish line in the middle, where the men from the coastal areas were. However, troops under John of Renesse rushed in to repel the invaders.
At this point the Count of Artois himself, leader of the French forces, crosses the brook, but while he's able to tear the Flemish banner, he suffers the sme fate as many of his men. His death is the beginning of the end for the French. The advancing Flemish forces slaughter the fleeing knights, solidifying their victory.
Source: http://www.liebaart.org/gulden_e.htm.