The Serb offensive against Srebrenica began in earnest on 6 July 1995. The VRS, with 2,000 soldiers, were outnumbered by the defenders and did not expect the assault to be an easy conquest. In the following days, the five UNPROFOR observation posts in the southern part of the enclave fell one by one in the face of the Bosnian Serb advance. Some of the Dutch soldiers retreated into the enclave after their posts were attacked, but the crews of the other observation posts surrendered into Serb custody. Simultaneously, the defending Bosnian forces numbering 6,000 came under heavy fire and were pushed back towards the town. Once the southern perimeter began to collapse, about 4,000 Bosniak residents who had been living in a Swedish housing complex for refugees nearby fled north into the town of Srebrenica. Dutch soldiers reported that the advancing Serbs were "cleansing" the houses in the southern part of the enclave.