What this apparent confusion of terms indicates is the diffi­ culty of applying a definition such as ‘international law’ to the customs of a society which did not think in terms of nationality. The distinguishing feature of a nation, as we understand the word, is its independent sovereign status, which makes it, legally, a unique and self-sufficient society. In legal theory, the kingdoms and principalities of the later middle ages were neither unique nor self-sufficient. The only society which was so was the society of Christendom, a supra-national society of which Christian kingdoms were dependent members. His al­ legiance to this society was the one overriding obligation of the Christian soldier. Various ties of personal loyalty might attach him to a whole series of secular masters; to one man, perhaps, he was bound by a sworn contract to serve him for a stated period, to another because he wore his order of chivalry, to others again by the tenure of fiefs. Each of these allegiances was based in an individual relationship, and for this reason conflicts of loyalty were a problem for the individual, defying resolution on the basis of any guiding principle of nationality. The only obligations which were universal were those which bound all Christian men alike, such as the rules of chivalrous conduct, for allegiance to the honour of knighthood was not limited by place or time. The rules of chivalry applied, in Ayala’s words, ‘wherever there was war’ .2