Well, whatever plan there was would have gone out of the window anyway when Jon Snow went LEEEEEEEEROY JENKINNNNNNS which Sansa specifically warned him about. Ygritte was right, he's brave but stupid. His stupidity nearly got him killed, and cost him apparently 100% of his cavalry and nearly all the infantry - made all the worse because Ser Onion suddenly decides that all their archers should also charge in the melee instead of, say, staying in the reserve and waiting until the bulk of Bolton infantry is committed and arrowing/charging them in the rear.
Also illustrated is how discipline and formations mean that a force consisting of even mediocre soldiers is infinitely superior to a horde of undisciplined warriors, no matter how "fierce". (There's also a terrible disparity in equipment to overcome, but come on, even wooden shields for the Free Folk would have evened the odds immensely.) The director in the making of videos is so focused on recreating Cannae - where two roughly similar armies met - that he forgets that for example in Alesia, Caesar's legions became surrounded by numerically superior Gauls and still came out on top due to their discipline. Ummm, now I will have to actually backpedal: Jon's army would probably not have fared very well even if everything had gone according to the original plan, if the Boltons had simply turtled down behind a shieldwall if they ever became surrounded.
Though, without Jon & co. tying up the Bolton infantry, a cavalry charge even by numerically superior Vale knights would have had a hard time trying to crack a square of pikes. Outside of
The Lord of the Rings, horses usually don't want to charge and impale themselves on a forest of sharp things pointed their way, so a cavalry charge should preferably be made to the flanks or rear. Though it takes iron discipine to have infantry hold the line when a wave of massive beast carrying heavily armoured knights thunders towards them, and preferably long and strong enough spears/pikes to take the impact (and outrange any lances the cavalry has) if some horses are foolhardy enough to press the charge home.
Also, who piled up all the bodies into a neat wall? We are shown that the dead are falling all over the battlefield, so they should have formed a roughly circular, quite flat disc on the ground, if even that.
Why didn't anyone have the brain to fell even a single tree so Wun Wun could have had an useful weapon with MASSIVE advantage in reach? (Because then there would not have been a Bolton shieldwall which the director apparently wanted.) EDIT: Ninja'd by PanzerKnacker
When cornered, why didn't Wun Wun simply grab a spear of a Boltonman by the shaft, he does have the reach for that easily? It's not like the other guy had had the strength to resist. (Was Wun Wun so afraid of sharp things too? Ah well, the answer is already above.)
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Was still epic though.
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To be fair, RamRam did have a few flaws in his master plan too: like Stannis, he apparently does not bother with scouts (who could have warned him about the approaching Vale host), and he callously orders the archers to volley an area where most of the combatants are his own (causing nearly 100% casualties to his own cavalry too) which should not exactly gain favours in the North. Somehow, I doubt that the Umbers' war cry "Who rules the North? WE DO!" refers to the Boltons in any way, so had Ramsay won, the victory would have been pretty short-lived.