Long ago, in the times of ancient kings and queens, there was once an island nation. This nation was ruled by a cruel man, whose heart was filled with hate, greed, and malice. That cruelty bled through to his military, who under his pleased gaze, would keep a firm grip on the populace, taking taxes and anything else he wanted while keeping them in constant fear.
However, despite all the gold and power he had, he wanted more, much more. To his powerful ego, all the world should be his to rule, with all its people his subjects. But he was hardly the biggest fish in the sea, as many much more powerful nations bordered his own, and if he tried to challenge them he would surely be conquered. So he was left with no choice but keep the peace, stewing in his own jealousy.
And then one day, something bizarre happened.
A mysterious pulse of energy washed over the kingdom, causing it to disappear from it's own world, arriving in a new land entirely. The king found that he was now neighbor to many new nations, that were home to all sorts of strange creatures. One of these new creatures were small colorful horses, who seemed to be mostly peaceful.
Upon seeing this new world, the king immediately saw it as ripe for the taking. He viewed the horses and other creatures as weak and vulnerable and thought they would be easily conquered. So he began a bloody campaign of conquest, seeking to bring all these animals under his rule.
In a surprise attack, he struck first against the outermost towns and villages, his army slaughtering all the little ponies that stood in their way; the king's military carved its way through this new world, leaving a trail of destruction wherever they went.
They were met with fierce resistance from the locals, who proved to be more of a worthy opponent than the king originally gave them credit for. The opposition had many tricks up their proverbial sleeves, such as what could only be described as magic. And while these strange powers their enemy possessed cost him countless men, he still refused to give up; his army continued their march on this world, causing untold death and destruction wherever they went.
And then the other races of this world became involved.
The inhabitants of the other nations must have realized that if the ponies fell, the king would attack them next. So it wasn't long before they joined in the fight, aiding the ponies against the king's army. Together, all the races worked as one to vanquish the invaders, quickly overcoming them.
The king's forces were pushed back to their island, much to his great displeasure. Soon, the ponies and their allies invaded the shores of his kingdom, and the king was left with no choice but to surrender.
After the war was over, the different races discussed what to do with the humans; eventually, it was decided to make them servants to the ponies and other species', believing humans too barbaric and dangerous to be free.
With the humans defeated and no longer a threat, things went back to normal as peace returned to Equestria and the other lands.
But if only the king could have known the events he'd set into motion...