In 1302, in the French campaign to subdue Flanders, the decisive battle was fought on a muddy field near the town of Courtrai.
The Supremacy of Cavalry Assured Over the past two years, French king Philip IV had appointed a French governor for the county and taken the Flemish Count "Guy of Dampierre" hostage. Unrest by guild members and city leaders led to a heavy hand, and many Flemish were removed from Bruges. On May 18, 1302, the enraged exiles enacted the Bruges Matins, a night where the illegal militia killed any Frenchman they could find, crushing the local garrison.
In retaliation, Philip IV launched an army of about 8,000 (2,500 of whom were cavalry) under Robert II of Artois, while the Flemish organized 9,000 well armed militia. While the French had a classical army, the Flemish were proud of their constant study and practice, considering themselves technologically, and thus militarily, superior. They fought unsuccessfully against the fortified French at Kortrijk on July 9 and 10, then came to face Robert's army itself.
The Flemish were well positioned as the field was not fit for cavalry charges being filled with ditches and streams. Servants were called to put planks in the depressions to allow the horses to charge, though many of the French wanted to attack as quickly as possible to put down the rabble. Robert held his ground and waited for the field to be prepared. While avoiding Flemish skirmishers, the infantry advanced, giving first blood to the battle. Robert began to call back the infantry to enable the proud cavalry to win the victory, but he paused at the condition of the field. He ordered the infantry to remain in assault until the cavalry would be able to make their own attack effectively.
When he pronounced the field of battle ready, the cavalry hit the Flemish lines powerfully. Though they held bravely, the French overwhelmed the Flemish, who attempted to flee but were cut down by the fast-moving French. The Battle of the Golden Spurs (nicknamed as such for the victorious cavalry) was won, and Flanders remained a grudging county under French rule.
With heavy cavalry proven effective, French knights rose to a new standard of haughtiness. In the Edwardian War with England, this would prove disastrous. The English, having been taught a harsh lesson by the Scots at Bannockburn about the effectiveness of attacking infantry against cavalry, used their longbows and infantry against the arrogant horsemen. As the Black Prince took Paris in 1347 (just before the terror of the Black Death, often called God's Punishment on the bloodthirsty men), he succeeded in his bid to seize the throne.
The enormous Kingdom of England & France would be a shock to the rest of Europe, but prove pleasing as it gave aid to Spanish conquerors and Austrian defenders against the Ottomans. Though the Joan Rebellion in 1429 nearly toppled English control, it would not be until the Tudor Wars that France would succeed in its break from England as Catholics made massive rebellion to Henry's divorce of Catherine of Aragon and break from Rome. The resulting conflicts would cripple England, which would bounce between Mary Tudor's return to Catholicism and her half-sister Elizabeth's religious vagueness. With only a ramshackle fleet, the English were no match for the Spanish Armada of 1588, which sailed into London and established Philip II of Spain as king. With England and even the Dutch subdued, Philip was able to rest on his laurels and manage the mighty Spanish Empire, on which the sun was never able to set.