The programme explained that the Mongul warriors were especially hard to overcome because if shot with arrows, they did not suffer such devasting injuries as their opononents as long as no vital organ was hit.
I quote here from the website of EduNet connect
"The Mongol army was based on lightly armoured horse archers. Under a quilted jacket or water-proofed leather jerkin, Mongol warriors wore a silk shirt. Even if an arrow penetrated their armour, unlike other cloth, the silk shirt would not tear but would wrap around the arrow head. This made it easier to remove the arrow and reduced the chance of infection. With cotton, wool or other cloth, bits of torn material would be driven into a wound making a dangerous infection likely."
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