If you want to see what a medieval Destrier was capable of, look at the white Lippen... (spelling!) Stallions. Most of their moves are claimed by their trainers to date back to natural horse movements that Destriers were trained to perform on command (and sometimes of their own free will) in combat. Biting, kicking, etc - the horse was about as destructive as a tank, and well capable of taking out lightly armed foot-soldiers before those damned 20 foot pikes became all the rage!

I have seen a clip of an old B&W movie (it was inserted in something else - I suspect it may have been originally from that Russian epic silent movie about the history of German Invasions) in which the fully kitted up horses and riders are lashing out at foot-soldiers around them - sweeping thru them like a scythe - freaky shot and one wonders just how many extras were hurt for real.

I have seen 16-18 hand high Shire Horses at the gallop - a hundred of them coming at you fully armed would definitely be brown pants stuff, and would seem like an earth quake - and if just 4 pulling a waggon at a fast trot could shake the ground under my feet that much... definitely a terror weapon!

A hand is 4 inches so 64 inches at the shoulder is BIG... the neck towers above you when they are on all fours - wouldn't like one to rear and lash its front feet at me - tin hat or not!