From the beginning of the Roman period, the steppe's fringe of Northern Syria experienced a strong sedentary expansion eastwards which reached its peak towards the end of Byzantine period. During the last two decades, the "Arid Margins Survey " has drawn a vivid picture of this gradual conquest. However, many questions remain beyond the reach of surface surveys, such as occupancy duration or differences between Roman, Byzantine or Umayyad occupation on a same site. The very phenomenon of this expansion is still to be understood. It may have involved massive immigration of sedentary people from neighboring countries as much as nomad herders settling down.