Over the course of four days in July 1995, Bosnian-Serb forces murdered more than 8,000 men and boys – in a United Nations-protected ‘safe area’. Legally recognised as an act of genocide, the Srebrenica massacre is the worst act of mass killing committed on European soil since the Second World War. What drove the perpetrators to carry out such a terrible crime? And how did the international community allow it to happen?