The so called third phase of the 100 years' war between England and France was kicked off by the English monarch Henry V., when he decided to invade France in 1415. After the initial invasion at Hafleur and sacking of the city. While technically a victory, Henry V. had lost about a third of his men and his troops were heavily plagued by dysyntery.

Therefore he decided to march to Calais, which was held by the English at the time, to regroup and replenish. Alas, as had to be expected from people getting invaded for the x-st time by the same enemy, the French did not watch idly but instead intercepted Henry at Azincourt. While he still commanded something between 6000-9000 men, the french numbers are a bit foggy. While contemporal accounts of 150.000 are definitely false, modern historians propose a number of between 12.000-36.000 French soldiers, outnumbering the English forces on their home turf. Apart from the numbers alone, the French seemed to have a clear advantage in regard to heavy muscle: While the English army consisted mostly of archers and only 1000-1600 knights, the French forces were made up primarily of knights and other heavy infantry.

The battle was to take place on flat terrain, which usually would have put mounted knights at an advantage. In this case however, the ground had just previously been plowed and rain had transformed the battlefield into a literal mud pit, which was also confined by forests on both sides, which made flanking maneuvers impossible and was a gift to the English in this case. The mud also meant that movements on the battlefield slowed down the French advance significantly and gave the English archers lots of time to get a headstart on their personal k/d ratio. For anyone wondering how heavily armored professional fighters perform while sunken knee deep into mud look like.

In short: France lost, suffering heavy losses and losing not only around 1500 regular knights but also many high-ranking nobles, including their commander in chief. The defeat delivered such a heavy blow to the French war effort, that Henry could not only continue his campaign but France had to subsequently accept the disadventageous treaty of Troyes.

Have you ever tried walking through a freshly ploughed field?

Now imagine doing it in full armour, while being shot at by English longbowmen.

Cmon bros. It's easy. French and their stupid cavalry. They probably got fucked because that stupid farmer dug a hole and horses got stuck under arrows. I'm not even googling shit