Season 7 of Game of Thrones already established that the White Walkers don't stand a chance against an army that knows its Achilles heel.

HBO announced that Game of Thrones is coming back for its final six episodes in April 2019. That being said, I've been rewatching the episodes a little bit at a time over the last few months to catch up a friend who stopped watching (life happened) back in season four. It's been a good refresher, especially where I think my theories of the Great War lie. For a while now, I've been thinking that there's just no way that the dragon-slaying Night King and his minions could ever be beaten. They bring a lot to the table, what with an ever expanding army of undead that rise from the living who are culled in ever-increasing numbers on the battlefield. However, the actual White Walkers are few in number, and apparently, all you have to do is kill the Night King and everything just dies. This plot device happened in the penultimate episode of season seven, when Jon Snow (attempting to capture a wight to take it back to King's Landing), was forced to use his Valyrian steel sword to end a White Walker who was leading a band of undead through a ravine. When the White Walker exploded into ice, all but one of the animated zombies also perished.
"Why do you think that happened?" someone asked Jon Snow. He replied, "Maybe that White Walker animated them. So when he died, everything he animated perished with him." Or something like that; it's not a direct quote. So that's the Achilles' heel of this whole plot. You kill the Night King, and the game is up. Sure, he's an obvious "Boss" within the rules well-established by video games, but could he stop a hundred dragon glass arrows? Could he best someone of Brienne of Tarth's sword ability (or Jon Snow's) wielding a Valyrian steel sword so that they don't get to cheesily unmake every weapon that you use against them? I think not. So kill that one guy...and the whole war is over. In modern terminology, if you sack the quarterback the game ends instantly.
So really, the White Walkers don't stand a chance. Imagine having the best army in the world but if you took out one leader who was always present on the battlefield, it was just game over instantly. Even with an ice dragon and an army of twenty thousand zombies, that just seems like really long odds. I wouldn't want to be on that side of a war. It's putting all your eggs in one basket, and it's just going to end up really bad for the White Walkers. This is especially true given that the Night King likes to strut around in the open with no shield or tank or anything. He just walks around, and he oftentimes can be found on a hill overlooking the battle. Could you paint a more obvious target on someone's back? Here...I'll place my most important piece that is the person who controls everything out in the open on this hill and he's just gonna stand there and make badass faces without any concern for shelter of any kind. I realize that in season 8, he may be on the back of a dragon which is significantly harder to get to, but Daenerys could always ram him with one of her dragons and when he fell off then all you'd have to do is shoot him with a hundred dragon glass arrows. If any one of them touched him, it's over.
So there you have it, unless something incredibly stupid happens, we already know how the Great War is going to be resolved. You are all welcome :).