Okay, so a long time ago, there was a big fight called World War II. Some people were being mean to others just because of where they came from or what they believed in. One group of people who were treated very badly were the Serbs. They lived in a place called Yugoslavia, and the bad guys, called the Nazis, thought they were not as good as the other people.
The Nazis did a lot of terrible things to the Serbs. They would take them away to special camps where they were treated very poorly. They didn't get enough food or water, they were made to work hard, and sometimes they were even killed. It was very, very sad.
The Nazis did all these terrible things to the Serbs just because of who they were. But that's not nice. Everyone should be treated the same, no matter what. Sadly, it took a long time for people to realize that, but now we know that it is wrong to be mean to someone just because they are different from us.