They will throw themselves down on the ground, leap up as you pass over them, stab your horses from below, seize your legs and try to drag you from your saddles, leap up on to the crupper behind you, and stab you to the heart.

This is what makes them so dangerous a foe to horsemen, and at Crecy they did terrible execution among the French chivalry.
"Therefore be careful, and wary.

Spit all you see on the ground, with your lances; and hold your swords ever in readiness, to strike them down as they rise up beside you.

Keep in as close order as you can, for thus you will make it more difficult for them to rise from the ground, as you pass over." He then formed his troop into two lines.

In the centre of the front line he placed the twenty men-at-arms from the castle, with fifteen of the tenants on either hand.