Even for modern man, the outfit of medieval knights often makes an indelible impression. It was much stronger in the "darkest" era (which, in fact, is by no means such). For almost a thousand years, knightly cavalry dominated the battlefields. During this time, the development of armor and means of destruction of manpower has passed a long and interesting way. So how could you defeat a war chained from head to toe in good steel?
On the "romance" of the old war
To begin with, artistic culture in general and modern mass culture in particular greatly distort the perception of the actual realities of any war. Including antique and medieval. And first of all, the works of culture "disfigure" the human idea of what the battles looked like. And although no researcher of military history can say with 100 percent certainty how this or that thing happened on the battlefield, the study of historical sources from equipment to lists of losses coupled with modern reconstruction by the forces of enthusiasts allows you to get some idea of how it could look in reality, and not in a movie or in the pages of a novel.
As a result, it turns out that real battles have about as much in common with their image in most works of popular culture as American wrestling and street fights have among themselves. All this must be understood before starting to speculate about how you can "kill a knight" in full plate armor. It should be understood that in the ancient and medieval war there were two main "sources" of personnel losses.
The first is sanitary losses: death from disease, injury, fatigue, and even old age. The second source of personnel losses is the massacre after the defeat of the army: if the worst happened and the army fled, and the enemy had a representative number of cavalry, then most often the massacre and capture of prisoners began. And although this happened often, not every battle ended in such a defeat. Most of the ancient and medieval battles are complex, hours-long and multi-stage actions. Most often, when the troops realized that the defeat was near, they managed to retreat in relative order. In the Middle Ages, when cavalry dominated the battlefields, even a panicky retreat most often did not allow the enemy to arrange a massacre (everyone just left!).
So directly in battle, as long as the troops maintained at least a semblance of formation and order, the losses were small. Victory in real battles was achieved primarily not by massacre, but by maneuver and maintaining the formation. If your formation broke, then subordinates, as a rule, began to scatter even before the enemy realizes that it is time to take prisoners and slaughter those who did not succeed. Such is the romance.
About armor and bottle openers
Of course, nobody wants to die. And therefore, throughout their history, people have created not only means of killing each other, but also means of protecting themselves loved ones. Armor has evolved most dynamically since the beginning of the Dark Ages. The invasion of Attila not only brought new peoples to Europe, but also brought stirrups for horses - a thing that will be destined to change the face of war for the next thousand years. The fact is that without stirrups, a man on horseback with a spear is not able to create a single destructive system, organizing a blow of monstrous force with the tip of a spear. It is possible to strike with a spear from a gallop so as to remain with a whole spine and arms only by adopting the correct stance in the saddle. And it is impossible to occupy it without stirrups.
It is the spear and stirrups that are the main weapon of medieval knights, and by no means a sword covered with the romantic veil of 18th century knightly novels. It is impossible to survive a blow from a stirrup with a spear. And the point is not even that such a blow will naturally pierce a person through and through. Even if the spear did not pierce, the embarrassing effect of the impact would be comparable to the impact of a blast wave. Therefore, the future knights quickly realized that they needed to defend themselves with multilayered clothing and chain mail. Actually, it was the latter that were the main means of protection in the Middle Ages until the XIV century. Only certain parts of the armor were plate: helmet, gloves, greaves. Although the latter two most often could only be afforded by the richest.
Classic plate armor appears very late, at the very end of the Middle Ages, and becomes the apotheosis of the development of knightly defense. It is extremely difficult to kill a person in such armor, but still not impossible. First of all, this was done by the same knights. A spear strike from a gallop with a sharp spear has a good chance of killing an opponent in armor, especially if the spear hits a vulnerable spot. It is extremely difficult to pierce plate armor with a bastard sword or ax. However, it is much more important here that the same embarrassing effect still passes through the armor and clothes under them, which can lead to concussion of organs and internal hemorrhage.
The surest way to kill an armored knight was to use throwing weapons, primarily crossbows. The race of the tensile force of these with the thickness and complexity of the armor is a separate story altogether. However, the crossbow bolt had an excellent chance of penetrating armor. And most importantly, crossbowmen were effective (like any arrows) from cover. The point was to bombard the knights with shots. Then the theory of probability began to work: at least something, at least at someone, at least at some vulnerable place, will fly. The advent of firearms by no means buried knighthood in armor, but became an even more sure means of killing an equestrian warrior in comparison with a bow and a crossbow.
Finally, the knight could be stabbed through a vulnerable spot with a knife, a sword, or a dagger. The main thing was to pull him off the horse first. For this, the infantry used special spears with hooks. Once on the ground, the knight most often could not do anything against the outnumbered infantrymen. Natives of the eastern and equine peoples also used a lasso - a rope with a loop for similar purposes.
But the main thing that killed the representatives of the military aristocracy was their financial situation. The fact is that all the knights were not uniformly equipped. Most of the fighters had fairly mediocre means of protection, others could have advanced, but not very high-quality equipment. Only the richest and most titled feudal lords could afford the best and truly super-reliable armor. Since such armor was extremely expensive. In terms of peasant labor, the production of one set of armor could be several years of work for all subordinates of the feudal lord.
Such is the romance. By the way, most often in feudal wars they still tried to take prisoners, since for any of the feudal lords or his military servants it was possible to get a decent ransom from the family in money, food or political preferences. Although, of course, there have been "bad wars" with massacres and mutual vendettas.
If you want to know even more interesting things, then you should read about why knightly sword a kind of "handle" is needed on the blade.