The Srebrenica massacre, when outgunned peacekeeping forces stationed around the town were unable to stop Serb forces from killing thousands of Bosnian civilians in 1995, taught the international community that a well-armed security force is essential to the success of a safe zone.
"To be effective, a safe zone requires a serious armed force that can defend it and serious logistics to supply it and that means a lot of military boots on the ground and serious commitment," Emir Suljagic, a survivor of the Srebrenica massacre who had worked as an interpreter for UN forces based in the town, told the Associated Press.
In practice, safe areas would require carving out a part of Syria from the sovereign control of the state and providing the military means to defend it. Safe areas could most easily be established and protected in open rural land, but the threatened civilians live in dense urban centers. Creating and protecting urban safe areas would require establishing military control over those areas, which is effectively equivalent to direct military intervention.