So I wanna talk about this because something I keep seeing mentioned in reference to "Party Pooped" is that the Yaks and their declaration of war did not actually pose a serious threat.
Personally, I think that that analysis is all wrong and--based on the information the show has thus far provided us--should a war between yaks and ponies break out, the yaks would ultimately win.
The comments to which I'm referring to may be wrong, or I may be wrong, or there may be no way to tell, but that's the fun part about forums. So, let's have a discussion about it.
First, I wanna talk about this assumption that Celestia, Luna, and alicorns in general have some godlike or incredible power and they alone would be enough to defend Equestria from almost any foe. I think this assumption is incredibly incorrect and that alicorns aren't as powerful as everyone thinks they are.
To start, let me bring up the point that in this history of the show, the alicorns have successfully defended Equestria twice, and failed to defend it every other time danger has presented itself. The first of these two times in particular are when Celestia defeated Nightmare Moon after her initial transformation, which was an occurrence of alicorn vs. alicorn and not something from which we can gauge relative alicorn power. The second time was when Cadance, combined with Shining Armor, defeated Chrysalis, a foe who had previously ousted Celestia. Cadance didn't even defeat her alone, she required help.
Ultimately, the Alicorns have been defeated more times than not; Chrysalis defeated Celestia in a matter of seconds, Twilight, wielding the power of all four alicorns, only stalemated Tirek, and Twilight couldn't stop a normal unicorn from escaping. The princesses were both take out by plants, for pony's sake.
Ultimately, despite the fandom seeming to believe that the princesses have godlike power, they've failed to consistently utilize any power they have to defend Equestria, and historically have relied on the Elements of Harmony, a resource which would not have been available at the time of the Yak-Pony War. To paraphrase Rainbow Dash in "Princess Twilight Sparkle Part 2", "Without the Elements of Harmony, how are we supposed to defend Equestria?"
"But what about the Rainbow Power they used to defeat Tirek?"
Well, I'll admit it's a possibility they could use that, but I find it to be an unreliable assumption to make seeing as they haven't displayed any ability to call upon that power again, despite situations arising where it could be used (i.e. The Bugbear attack or when Pinkie came face-to-face with that arctic beast).
The second thing I'd like to argue is that the fandom seems to assume that the average pony would be more valuable than the average yak as a soldier, considering the flight and magic. What the fandom seems to be forgetting is that this is not the human world, and those skills are considerably more common-place. Unicorns would barely have any magic at all applicable in a war environment, as Twilight said herself that the average unicorn can only use a little bit of magic relevant to their Cutie Mark. Additionally, we have no reason to believe that yaks DON'T have magic, they simply never displayed the use of any.
While I don't have any reason flight wouldn't be useful for war (it very much would) the yaks live in a world inhabited by Pegasus, Griffons, Changelings, etc. They must be used to dealing with flying enemies and have developed anti-air weapons, considering they are historically warmongers.
"What about ponies that are especially adept at magic, like Twilight, Trixie, and Starlight?"
They would probably be the biggest opposition to the yaks, alongside the alicorn princesses (who I would weigh to be generally their equals in terms of offensive strength, give or take). But they alone cannot fight an entire army. They would put up a good fight, but they would ultimately just be flat-out outnumbered. Heck, Twilight plus five friends took their sweet time dealing with a flying bear. An army of weathered soldiers would destroy any small line of spellcasters.
Which brings me to my third point: YAKS ARE HISTORICALLY WARMONGERS. This was stated by Applejack in the recent episode. I mentioned the comparison of the average yak to the average pony earlier in the context of soldiering, but that's just it: the average yak IS a soldier, while the average pony isn't. Yaks have much more experience (as far as we know) waging war than ponies. While it is true that the pegasi were originally a militaristic society (as displayed in "Hearth's Warming Eve") that was a long time ago and based on what we have seen of modern pony society, that nature has been abandoned. While it is also true that the Royal Guard exists, we have only seen them engage in war-like activity once, during the Changeling invasion of Canterlot. They lost big-time. While I'm not saying it would be a one-sided slaughter, I'm saying I'd place my bets on the yaks to ultimately beat the Royal Guard.
Those are the three main points I wanted to make. In summary: I think the yaks would beat the ponies in a war, and I've based my argument on the information we can take from the show so far. This is a forum thread, of course, and I'm completely open to discussion and friendly argument, so let's talk about it. Who do you think would win, and why?