In 1912 Sterling Armure enlisted in the British Army, spending his first year of duty stationed in East Africa before being transferred on the outbreak of war in 1914. After two years of bloody fighting, his Regiment goes over the top in Flers-Courcelette into heavy German resistance when large clouds descend from the German lines.

Armure awakes after the apparent gas attack not in the muddy fields of Flanders, but a pristine forest. However, that is not the only change as both he and a number of the displaced soldiers in his Regiment have been turned into Ponies.

Lost in unknown territory, Armure is sent with a patrol to investigate a nearby village.

But why does everything seem familiar?

AU where a number of colts were transplanted from Equestria to Earth before WWI. Most have lost their memories but they return slowly once back.

Minor crossover with Blackadder.