Ishval was an eastern region in Amestris, inhabited by the Ishvarites, a race of people with dark skin an red eyes which worshipped Ishvala, their absolute one god of creation. According to the official records, these strong religious values came in conflict with the rest of the country, and incidents between people of different ideologies where more and more usual.

In 1901, a military officer shot an Ishvarite child by accident and an enormous civil war erupted. Riot after riot, the rebellion expanded through the whole eastern Amestris area and soon no one could see an end to the war. Seven years passed between offensive and defensive warfare. Then, in 1908, fuhrer King Bradley, sole ruler of Amestris, set a new military operation in motion.

     

And so National Alchemists (alchemists with a certified license who serve the military) where dispatched to the front to serve as human weapons. The goal was probably not only to put a definitive end to the endless war, but to also test their practical usage on the battlefield. By next year, after the annihilation of most of the Ishvarite race, the war had ended.

Roy was one of those human weapons. He was serving as major and was only 23 years old at the time. Being thrown onto a battlefield, at such a young age, and after enlisting himself out of hope for the future and conviction for a better world, we can get a rough idea of just how deeply it affected him. His alchemy especiality being the control over fire, it's heartbreaking to observe just how up close he witnessed all the killings he comitted. All of this would be enough to break an idealist man such as Roy.

Roy is also haunted by his inability to protect everyone, something that was the foundation of his dreams. However naive was that desire, it was still a shock for him to see it so thoroughly crushed. Still, some of his subordinates took the time to assure him that, even if not everyone, he was still able to protect a handful of people, including them. It was because Roy was there that people like them managed to survive. And that, however small, is something.

The fact that he was able to overcome all of this and still keep going, it's proof of just how strong his will is. Roy is a man of future, and as such, the only way for him was to pick up his pieces and reinvent himself and his ideals. After that, he just needed Hughes to give him a little kick to let him know he wouldn't be alone if he attempted to reach the top. The rest is (or will be) history.