In July 1995, Srebrenica was a besieged city that the UN had declared a protected zone. But when the city was captured by Bosnian Serb forces, there were only 400 soldiers from the UN squad in place - and the promised protection was not there.
Women and children were bused out of town while men and boys were taken away to meet their deaths. From July 11 and about ten days onwards, 8,000 boys and men are estimated to have been executed and thrown in mass graves.
In the video you can see a brief summary of what is called the largest genocide in Europe since the Second World War.