In 1939, Equestria was teleported from Equus to Earth for unknown reasons. In the meeting with the human leaders, Celestia says that all humans must convert into ponies to rid their war-like nature so they can live in peace and harmony among all of ponykind. After her proposal is rejected, the princess seals Equestria inside a magical barrier where she and her subjects live in isolation for 12 years. In 1951, ponies attacked major human cities across the world, determined to convert humanity by force, thus starting a conflict that would come to be known as the Conversion War.

Over the following years, the war rages around the globe, claiming the lives of thousands from both sides. The humans fight fiercely against the pony invaders with the help of the pony resistance fighters, willing to do whatever it takes to defeat Equestria and eliminate the pony threat. Celestia and her fellow princesses continue their campaign of converting humanity but due to severely underestimating the human resistance, the war is at a stalemate. Changing their strategy, ponies launched a massive invasion of the United Kingdom, overwhelming the British defenses and taking the southern territories, their plans and intentions remaining unknown.

In 1957, the United States decided to send 12,000 troops to aid the British and prevent the UK from falling, hoping that it would mark the turning point of the war and finally allow humanity to take the fight to Equestria. Among them is one human soldier and pony resistance fighter whose actions over the following years will determine the fate of all of humanity. This is their story.