It is tempting, and not totally misleading, to attribute the longevity of many empires to the military advantage of a large and powerful state surrounded by much smaller states, or tribal territories. Whilst empires may be briefly built on military advantage alone as, perhaps, was that of Alexander the Great, the longer- lasting examples can be attributed not only to military size but also to the advantages of a 'civilized' culture in the literal sense, means a society centred on relatively large urban centres containing specialised personnel who contributed technical and organisational advantages to the empire. The prestige and self-esteem associated with such systems may well help them to survive. Certainly the ruling groups of the Chinese, Roman and British empires were all firmly convinced of the superiority of their cultural inheritance, and successfully imparted this ideology to many of their subjects and neighbours. However this conviction did not prevent such systems from adopting and adapting to useful features of surrounding societies.