Because arrows *can* penetrate plate armor if the end's sharp enough and it's shot with enough force.

They used a *hit and run* method where they shot arrows while their horses were running the opposite direction and they were being chased by the lancers. They also ran their horses in circles and shot arrows in the direction of the enemy so they couldn't be caught. The west never fought with this tactic before. They usually just had two armies clash and fight a battle of strength and will.

Light armor and accuracy always defeat heavy armor and strength. The cavalry would have done better to equip medium armor to protect the chest and neck, and adopt a lighter, quicker cavalry and close-range weaponry.

John Kerry?

The never fought the Wests knights, they only went as far west as the Ukraine.

Heavy cavalry of the time was mainly used as a weapon against dismounted archers, and were not very effective against highly mobile mounted archers. Also, heavy cavarly was only a small component of armies of the period. Most of the troops the mongols faced were light infantry forces.

The Mongols were one of the first major armies to effectively employ manuever warfare, which allowed them to move around the battlefield rapidly and engage their enemies were they were weakest. This allowed the Mongols to fight on their terms, playing to their strengths. Furthermore, the highly accurate archers, equipped with recurve composite bows, were able to pierce plate armor. The energy of the arrows the Mongols fired was comparable that of one fired from a longbow.

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Another factor is that the Mongols preferred fighting in the winter when their foes were weakest. Tough Mongols would relish the cold weather while their softer city-bred adversaries could barely function

They would use the frozen rivers of Eurasia as a roadway system to attack the cities along them.

The Mongols were also experts with siege engines, so they could utterly demoralize a foe through terror tactics and surprize attacks.

Plus their iron/steel headed arrows could most definitely penetrate armor and shields. Some sources cite kills from hundreds of yards, although this was likely from indirect fire, not sniper shots.

The bows that the Mongols used were composite bows, and were extremely powerful. They had a draw almost as great as a longbow at half the size. They also had a greater range, with some estimates at 350 yards (compared to a longbow's 250).

Most European soldiers at the time either had chain mail armor or plate armor that was of somewhat low quality, since plate was expensive to make. A Mongol bow could easily penetrate these types of armor. In addition, a lucky shot to the neck or the armpit could kill a knight in good quality armor.

The Mongols also had heavier cavalry to deal with enemies after the light cavalry had shot them up. They carried lances and axes, and could penertrate the European's armor up close.

And when they couldn't kill the knights, they just shot the horses. The man in the big metal suit isn't going anywhere fast without a ride.

Genghis, was fighting in the roman era, not in the middle ages there a few years between them, about 1000 years , you duff ass, and no bow is better than the English long bow, you need to pull 300lb for the full one, with a bodkin arrow head its capable of penetrating a one foot thick tree trunk at 100 yards, just ask the french