THE BANTU OF KAVIRONDO 227
for waging war. But beyond this immediate motive the taking of life served other purposes, which become apparent when the whole organization of warfare and the groups that waged war with one another are subjected to a closer analysis. Although between most tribal groups in Kavirondo—especially those who lived in a permanent state of hostilities—an uninhabited zone of a few miles' width was maintained, the tribal territory did not remain static, but either expanded or contracted as the result of extended periods of warfare. Among the Logoli the conquest of new land for cultivation is expressly stated to have been one of the chief motives for warfare. It does not, however, become apparent as an immediate motive, as a war expedition was never terminated by the annexation of a given area by the victorious side and a readjustment of the bojindary line confirmed by the vanquished or any similar procedure. This would have required a much firmer military organization than existed and an organized protection of the borders, for which the political structure of the tribal groups was much too loose. The immediate result of a raid was rather to weaken and intimidate the neighbouring tribe and to induce its members gradually to retreat, so that the uninhabited zone would widen and the grazing of stock and the cultivation of gardens could safely be carried on in what was formerly no-man's-land. The territory thus gained by a very gradual process came under the control of the clan whose warriors had driven the enemy tribe into retreat and was shared out among them.
Whether such, a conquest of territory involved a real expansion of the tribal area or whether the gaining of land on one side was always accompanied by a lo*s on the other side is very difficult to decide. As far as traditions go, it appears that changes in the territory held by the various tribes were due partly to a general tendency of an eastward migration caused by a pressure of the Nilotic and Teso-speaking groups, the ultimate reason of which would have to be traced back to the upper Nile Valley, and partly to a real need for expansion. This need, again, arose from a variety of causes. Of these the most important seem to have been (a) a natural increase in population which, in view of the fecundity of the Bantu people, must at times have been considerable even in pre-European days; (b) an increase in the wealth of cattle, either by natural increase or by conquest, requiring larger grazing areas; and (c) the deterioration of the soil, owing to various forms of