The Roman imperial army was unrivalled until recent times in its professional structure, efficient training, detailed organization, and ordnance support. It was remarkable in an age of poor communications and limited technological advance. The army sustained a great empire militarily and politically. Firstly, its skill and success ensured Rome's domination, and secondly, the loyalty of the troops ensured the political survival of the emperors, who sought to preserve the fabric of government and make it work. The army was a vital element in the subsequent development of western civilization. The large number of soldiers and their associated dependents meant that they had a large impact socially, economically, and culturally on the settlements that grew up round the camps and on some of the communities where they settled after discharge. The privileges of the soldiers set them apart from other men of their social class, and the enhanced position of veterans established them as a very important group in their own right, an integral part of the whole phenomenon of Roman "government". The study of the Roman army therefore embraces not only military but also political, social and economic issues.