Okay, I will preface this by saying that I loved the episode and military tactics in no way will detract from my overall enjoyment of it. Plus, I am only an armchair general with zero military experience, but I have read many leatherbound books. That being said, we begin with the airing of grievances. I got a lot of problems with you Winterfell people and now you're gonna hear about it.
— What the hell was the plan with the Dothraki anyway if Melisandre hadn't shown up to ignite their blades? They were going to ride into a head-on assault on the Army of the Dead with no recon of what they were attacking and conventional Arakhs (their curved swords) without any dragonglass, Valerian steel, or flame? Arakhs are slashing swords, so at best you're going to slash clean through some of the bonier Wights and behead some but that just slows them down a bit, and any losses of their will be made up for by them resurrecting your dead.
Once Melisandre ignited their swords (something they had no idea was going to happen in advance) it did seem like they might have been responsible for killing a lot of the giants in the AotD, since we saw dozens when they came through the Wall and several in their charge, but only one made it into Winterfell for Little Lady Badass to kill.
The Dothraki are purely an offensive force. They don't protect fortresses, they're nomadic conquerors. So I get where charging is pretty much the only thing in their wheelhouse. But they could have done it smarter. Like have them serve as scouts to recon the AotD's frontlines with flaming arrows to light things up while staying out of range, to determine that oh, yes, holy fuck, they have giants and a four-layer dip of zombies rolling in a wave towards us. Those recon attacks would have drawn the AotD to attack in return. And you use the Dothraki cavalry to lead them in a tactical retreat to where you want them to go while staying just out of range.
— Where you want the Wights to go is to create bottlenecks using an outer ring of the flaming trenches that is always burning (none of this waiting for Ser Davos in Air Traffic Control to signal Daeny and Jon in a blizzard which he knew the Night King could bring) but with gaps in it for the Dothraki to ride though and go back behind your lines (the second ring with differently placed gaps that s located close to Winterfell can remain unlit until needed as it did). Then you bombard the exit gaps with as much pre-sighted flaming trebuchet and catapult and flaming dragonglass arrow fire as possible to start building up a massive pile of Wight bodies. The gaps correspond to the strongest points in your defensive wall around Winterfell and where you have your most disciplined troops (the Unsullied) with shields and long pikes to engage the enemy at a distance to kill any Wights that make it over the pile of corpses which is getting steadily bigger.
The Dothraki meanwhile have swung around from another gap in the side and have looped around to attack the AotD's flanks with flaming arrows as they ride up and down their lines just out of grabbing range. If any of them should be knocked down, they'll have dragonglass blades to defend themselves. This all keeps the AoTD contained and heading toward the bottlenecks at the front, building up the mountains of bodies and making it harder for them to advance. You use their numbers advantage against them as it contributes to building up the piles of bodies.
— Why were no anti-dragon countermeasures created? They put all their eggs in one basket with hoping Daeny and Jon would be enough to stop the Night King and Visarion. They would have been even more screwed if Visarion had started burning their armies on the ground. Maester Khyburn's Scorpion which they encountered in battle last year is not some complex secret weapon, it's just a average-sized ballista. The Northern trebuchets were way more complicated. They should have been able to build Northern knockoffs of the Scorpion complete with dragonglass-tipped bolts to use against the Ice Dragon, and mounted them on the ramparts of Winterfell, and especially around the Godswood where the expected the Night King to come for Bran. But then again, Jon was stupid enough to come down and land on the Godswood wall in low visibility just to check things out knowing full well they were expecting the Night King to show up there, so his ass probably would have been toast if not for the plot shields.
— Why was Ghost running with Jorah and the Dothraki headlong into the Army of the Dead? What the fuck is he supposed to do there? Biting and clawing Wights does jack shit, especially when you've de-Hulked and are only normal wolf sized rather than direwolf sized because of a limited CGI budget. Ghost should have been defending Bran in the Godswood where he could sense the Whitewalkers coming first, Bran could warg into him if need be to recon the area or at least be a nuisance to the Whitewalkers before being killed. Somehow he survived that charge into the AotD and the subsequent battle (he just disappeared for the rest of the episode) and is back in next week's episode.
— Much love for Theon's defense of Bran here, and he really redeemed himself, but seriously, given his track record for betrayal and cowardice, was he and the Ironborn the best choice by themselves to defend Bran? I get as part of a larger contingent, but with no one else to oversee things? I mean, trust but verify. They also left young Alice Karstark, who got killed offscreen, but is also from a family that betrayed the Starks, which is not her fault, but still. I know they have limited resources, but this might have been a good place for Tyrion and Sansa to have an overwatch in a tower so they could see the battle and the Godswood and call for reinforcements if necessary and change the battleplans if need be. Also knowing Sansa was there would keep Theon in line if there was any doubt in his resolve.
— I can not say enough how stupid it was to hide civilians in the crypts. And this is not 20/20 hindsight because I was saying it here online before the episode aired in the other thread upstairs. They knew the Night King could raise the dead. They knew the Night King was likely to come to Winterfell to go after Bran in the Godswood. So what possible reason would you have to put people in a crypt except to serve as a plot device?
The wights are held together and able to move by dark magic despite having no muscles or ligaments and looking like fighting skeletons out of Jason and the Argonauts sometimes, so there must be some kind of force animating them and giving them much more power and mobility than their corpse itself should provide. They fall off cliffs and get right up. They move at faster than human speed in a tidal wave of bodies that topples thick wooden stockades and rolls over armies. Kicking through the thin stone sides and ends of some old crypts doesn't seem out of the realm of possibility.
The civilians should have been waiting in a stronghold somewhere to the south. If no one came for them from Winterfell after a day they should take what provisions they can carry and march south as fast as they can, hoping to stay ahead of the Dead and that someone will show them mercy along the way. Unlikely, but staying at Winterfell meant almost certain death.
I was a little disappointed in how they portrayed both Sansa and Tyrion in this. Tyrion pouting about not being taken seriously is not all that unusual, but he could have insisted on serving in the battlements. Daenarys would have eventually given in. It really made no sense for him to be down in the crypts where he could give no advice. This was an all of nothing situation. If they lost they were dead. You don't leave a decent tactician somewhere he can't help in that situation, even if he is your future brain trust. And Sansa provided leadership and words of encouragement to frightened civilians even as a child during the Battle of the Blackwater when Cersei would not. Yet here she did less to comfort or lead her own people to safety when the dead started rising than Gilly and Varys did. Still love Sansa, but not the way she was written in the episode.
— Jon, you noble idiot. You always run flat out at that undead fucker from the get-go. Don't do any dramatic pauses for a stare down, because you know he's going to "raise the roof" and resurrect the dead. I still feel Jon could have even barreled through that last twenty feet of Wights and killed the Night King anyway if he hadn't just stopped. They can't zombify you with biting, they can just nibble at you, so plow through the fuckers and stab him. Seriously, Brienne was being eaten by Wights continuously from the start of the battle to the end and she survived. In Red Wedding-era GoT Jon's ass would have been dead right there once he stopped running and chose to fight the undead horde rising around him, but thanks to plot shields and super accurate fire support from Daenarys and Drogon that can burn Wights directly next to him in all directions but not even singe Jon's Perfect Hair, he survived.
— So, besides being John McClane in Die Hard II and fruitlessly waving torches at passing aircraft/dragons that couldn't see him until they lit the runway/trench on fire, what was Ser Davos' job during the battle? Because it seemed like he was in charge of giving long intense stares at people and picking inappropriate times to try and execute Melisandre in the middle of a fucking battle. Like, she was second runner up for MVP of the night after Arya, dude. I know you can barely read, but read the room. Killing her would have been as stupid as letting those ghosts under the mountain go free in Return of the King after just one battle. I'll hold your oaths fulfilled when you finish this damned war, you tactical advantage having motherfuckers. The Battle of the Black Gate would have been over within minutes with their help. No deus ex eagles needed.
— Unless Melisandre's trip to Volantis included a sidequest to pick up the Second Sons from Mereen and the other Red Priests and Priestesses to fight on Daenarys' and Jon's behalf (and some other fleet besides Yara's to transport them, since they're leaving from the Iron Islands in the next episode), I'm not sure how the hell they're supposed to defeat Cersei's superior Golden Company army, Euron's navy, and the Kings Landing garrison without burning the armies, Euron's fleet, and the Red Keep to the ground with the dragons. The prophecy of the dragons burning the ceiling of the Red Keep and snow falling on the Iron Throne is about to come true.
Cersei might just go full Mad Queen and blow it all up anyway with the wildfire under the city, killing all the civilians in the process.
So I anticipate a major battle in the field and sea to serve as a distraction for some kind of stealth mission to assassinate Cersei and take the Iron Throne with minimal civilian casualties, perhaps with Jaime becoming Queenslayer this time when he sees what she's planning to do or Tyrion, since it's one of her brothers that is prophecised to kill her. But it doesn't quite work out and Danaerys has to come in on Drogon anyway. Either Drogon or Rhaegar gets taken down by one of the many Scorpion weapons they've established on the perimeter walls.
I have more thoughts about the dramatic side of the episode, but that'll do on the military aspects of the episode for now. I know, TL;DR, blah blah blah.