Why Equestria Would Win a War Against the Yaks (And How!) · 12:07am Dec 17th, 2016
The situation-The Yaks declared war on Equestria after the Episode That Shall Not Be Named.
The combatants-The Holy Empire of the Equestrian Nation, the Crystal Empire, (possibly) the Kingdom of Griffonstone vs. The Principality of YakYakastan. Unknown allies of the Yaks (if any. Seriously, who wants to hang out with these @$$holes?)
The Result-Unicorns have magic shields strong enough to defend entire cities as well as other unknown abilities, Pegasii fly and control the weather and Earth Ponies have a preternatural level of strength. The strongest among them can shatter solid stone. If Griffons choose to participate with the rest of the Empire then their are two flying races on the Equestrian side. The Ponies have a culture which prizes cooperation, teamwork and harmony. This is a point in Equestria's favor as this would do wonders for morale. Also, the Crystal Empire would absolutely join on the Equestrian side. As the Season 5 finale shows, the Crystal Empire military is able to challenge and even overcome the Equestrian Military. They would easily defeat the Yaks. The Yaks would have to go through the Crystal Empire in order to invade Equestria. If, by some miracle, they did so successfully they would still face serious opposition from Equestria.
The Pegasii could summon perpetual storms on the Equestrian border. How the Yaks would get through this is anybody's guess, but let's presume they did so. Apparently, the Crystal Ponies did or in that timeline Pegasii didn't try that strategy. After getting through the Pegasii created storms they would face the charge of Unicorn magic and Earth Ponies powerful enough to crush rocks beneath their hooves. While battling through that, they would face Pegasii and maybe Griffons swooping down and cutting through their ranks.
Eventually, they would simply surrender rather than face utter annihilation and Equestria's empire would have a nice, new northern province. On a related note, how did an army that was 1000 years out of date manage to hold its own against the modern Equestrian military in the season 5 finale?
Result-Equestrian victory.
Vivat Sol Imperium
'cause reasons', of course!
No need to even posit a clash of armies. Such a war would be determined entirely by logistics. There is one known pass that goes between Equestria (via the Crystal Empire) and Yakyakistan. The rail network doesn't go there, but yetis do. That's one heck of a supply bottleneck for the yaks, with the Crystal Empire being one heck of a cork at the end.
As King Varian once said to Warchief Vol'Jin: