from the Saracens, he adopted the same method of holding the foe at arm’s length.  He seized Old Castile as far as the River Duoro, but the rest of the province south of that stream he converted into a waste boundary by transporting the Christians thence to the north side, and driving the Mohammedans yet farther southward.[345] Similarly Xenophon found that the Armenian side of the River Kentrites, which formed the boundary between the Armenian plains and the highlands of Karduchia, was unpeopled and destitute of villages for a breadth of fifteen miles, from fear of the marauding Kurds.[346] In the eastern Sudan, especially in that wide territory along the Nile-Congo watershed occupied by the Zandeh, Junker found the frontier wilderness a regular institution owing to the exposure of the border districts in the perennial intertribal feuds.[347] The same testimony comes from Barth,[348] Boyd Alexander,[349] Speke,[350] and other explorers in the Sudan and the neighboring parts of equatorial Africa.

[Sidenote:  Border wastes of Indian lands.]

The vast and fertile region defined by the Ohio and Tennessee rivers, lay as a debatable border between the Algonquin Indians of the north and the Appalachians of the south.  Both claimed it, both used it for hunting, but neither dared dwell therein.[351] Similarly the Cherokees had no definite understanding with their savage neighbors as to the limits of their respective territories The effectiveness of their claim to any particular tract of country usually diminished with every increase of its distance from their villages.  The consequence was that a considerable strip of territory between the settlements of two tribes, Cherokees and Creeks for instance, though claimed by both, was practically considered neutral ground and the common hunting ground of both.[352] The Creeks, whose most western villages from 1771 to 1798 were located along the Coosa and upper Alabama rivers,[353] were separated by 300 miles of wilderness from the Chickasaws to the northwest, and by a 150-mile zone from the Choctaws.  The most northern Choctaw towns, in turn, lay 160 miles to the south of the Chickasaw nation, whose compact settlements were located on the watershed between the western sources of the Tombigby and the head stream of the Yazoo.[354] The wide intervening zone of forest and canebrake was hunted upon by both nations.[355]

Sometimes the border is preserved as a wilderness by formal agreement.  A classic example of this case is found in the belt of untenanted land, fifty to ninety kilometers wide, which China and Korea once maintained as their boundary.  No settler from either side was allowed to enter, and all travel across the border had to use a single passway, where three times annually a market was held.[356] On the Russo-Mongolian border south of Lake Baikal, the town of Kiakhta, which was established in 1688 as an entrepot of trade between the two countries, is occupied in its northern half by Russian factories and in its southern by the Mongolian-Chinese quarters, while between the two is a neutral space devoted to commerce.[357]