To anyone familiar with the comics, there was a story arc called "Feats of Friendship" which involved the daughter of king Diomedes, the tyrannical ruler of the island of Thrace being sent out to the Feats of Friendship tournament to sabotage and destroy the friendships between both the ponies and the races they are allied to. This conquest never comes to light as she realizes how powerful friendship is and stops sending reconnaissance reports back and effectively betrays her father.

Their motives can be best shown in these two pages:

But what if they actually did carry out their conquest of Equestria? What would the war between Thrace and Equestria look like and how would it unfold? how bad could it have gotten?

I don't think that there is any real way to gage that. We know almost nothing about Equestria’s population, military size, level of defensive preparedness, etc.

If I were to guess. It would go something like the Changeling Land's invasion of Equestria in Hearts of Iron Equestria at war. Where a smaller, but more professional and more prepared military invades Equestria and the Equestria initially takes devastating loses, but as the war goes on and the Equestria’s military reorganise and their war industry pick up momentum, the tide will turn and Equestria will probably achieve victory.

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I don't think it would end well for Thrace considering that the Equestrians are more familiar with their territories than Thrace would be, not to mention their Changeling allies would most likely leak information to them and sabotage Thrace's war efforts.

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I think the war between the two countries will end up similar to the invasion of the Soviet Union by Germany during Operation Barbarosa.

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So much for trying to p[rove that Friendship is weakness. If his plan to sabotage the Feats of Friendship tournament succeeded, it won't destroy the friendship between ponies and other races as he expected but would instead collectively piss off Equestria and incur their wrath upon his small island kingdom.

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Even not factoring in the various races that are currently allied with Equestria, his plans would still fail. After all, a small island taking on a big nation has never turned out well.

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based on those two pages, he's definitely delusional. somehow thinks he can conquer equestria but doesn't have any powerful magic like with other villains.

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Thrace seems to be at around the antiquity period of development. Equestria is more advanced than they are, so I don't understand why they're so confident that they could taker on a larger and more powerful nation.

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and in My Little Pony fashion. Twilight and the mane six manage to demonstrate how powerful friendhsip truly is and get the entire population to undergo a heel face turn. Diomedes and possibly the rest of Swift Foot's family will not reform like the rest of their kingdom. refusing to accept defeat and admit that their view of Equestria and friendship is wrong and would flee from Thrace. Continuing to hold on to his delusion and swearing revenge similar to Chrysalis after her hive went into a similar heel face turn.

later on, he earns a seat in the Legion of doom in season 9 and gets petrified liek the other villains.

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Britain seemed to do quite well for themselves.

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problem is thrace is not britain.

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he's definitely delusional

Okay NOW you have a story idea on your hands.

He wants to start the war. All his court and family know he's insane and they will get destroyed but are too afraid to act.

Swift Foot recruits the Student Six to help her overthrow her mad king father. Cloak and dagger ensues, the story ends with Swift Foot on the throne and a new era of peace, prosperity, and friendship dawning.

...I could write this. I should write this.

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This should also be about Equestria learning of the Thracians and wanting to make peace and forgive this lost fourth tribe and making up for not expressing friendship to them and leaving them in the cold when migrated to Equestria thousands of years ago. Showing collective guilt that it was partially their fault that Thrace became such an antagonistic force.

It would also ultimately about saving Thrace from itself as she knows that Thrace has no chance of surviving a war with a bigger and more powerful nation. It will be wiped out if Diomedes carries out his invasion plan which would inevitable fail due to his underestimation of the power of Friendship.

Yes, write it. I've seen other unfinished fics regarding Thrace and they also point to war breaking out between them and Equestria.

I have already seen some fanfics exploring Thrace after the events of Feats of Friendship and from what i've ready they also point to the same outcome of war breaking out between Equestria and them. and I know personally that they will not survive the full wrath of the Alicorn Sisters.

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My thoughts were going to the conflicts with Hawaii and Japan when I typed that comment.

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though i did find some unfinished fics exploring thrace and diomedes. Though unfinished, they seemingly pointed to war between them and Equestria as being an outcome. A war that I am sure Thrace has no hope of winning.

The other villains had a special power that made them a threat. What does Diomedes even have? nothing.