Hey kiddo, so a long time ago, in a place called Thrace (which is now part of Bulgaria), there were some people called the Thracian Bulgarians. They were a group of people who lived there for a really long time and had their own language and culture.
In 1913, there was a war between Bulgaria and some other countries around it, and Bulgaria ended up losing. When they lost, they had to give up some of their land, including the part where the Thracian Bulgarians lived.
The people who took over that land didn't like the Thracian Bulgarians and didn't want them to live there anymore. So they did some really mean and horrible things to them, like forcing them to leave their homes and taking away their things. Some of the Thracian Bulgarians were even hurt and killed just because they were different.
It was a very sad and unfair situation, and many people today still remember and honor the Thracian Bulgarians who suffered during that time.