HINDU KUSH, a range of mountains in Central Asia. Throughout Soo m. of its length, from the Pamir region to the Koh-i-Baba, west of Kabul, it forms the water-divide between the Kabul and the Oxus basins, and, for the first 200 M. is the southern boundary of Afghanistan. Probably it branches from the head of the Taghdumbash Pamir, where it unites with the Sarikol stretching northwards, and the impressive mountain barrier of Murtagh, the northern base of which separates China from Kan jut. The Wakhjir pass, crossing the head of the Taghdumbash Pamir into the river Hunza, almost marks the trijunction of the three great chains. As the Hindu Kush strikes westwards, after first rounding the head of an Oxus tributary (the Ab-i-Panja), it closely overlooks the trough of that glacier-fed stream under its northern spurs, its crest at the nearest point being separated from the river by a distance of about io m. As the river is here the northern boundary of Afghanistan, and the crest of the Hindu Kush the southern boundary, this distance represents the width of the Afghan kingdom at that point.
Physiography.—For the first 1 oo m. the Hindu Kush is a comparatively wide flat-backed range with small lakes on the crest, and possessing no considerable peaks. It is crossed by many passes, varying in height from 12,50o ft. to 17,500 ft., the lowest and the easiest being the group about Baroghil. As the Hindu Kush gradually recedes from the Ab-i-Panja and turns south-westwards it gains in altitude, and prominent peaks rise to more than 24,000 ft. above sea-level. The main central water-divide is not the line of highest peaks, which line is farther south, where Tirach Mir dominates Chitral from a southern spur. For some 4o or 5o m. of this south-westerly bend, the crest is intersected by many passes, of which the most important is the Durah group (including the Minjan and the Mandal), which rise to about Is,000 ft., and which are practicable links between the Oxus and Chitral basins.
From the Durah to the Khawak group of passes (1 I,000 and 12,000 ft. in altitude), the water-divide overlooks Kafiristan and Badakshan. Here, its exact position uncertain, it lies amidst a wild, inaccessible region of snow-bound crests, and is nowhere less than 15,00o ft. above sea-level. The Khawak, at the head of the Panjshir river, leading straight from Badakshan to Charikar and the city of Kabul, is now an excellent kafila route, and is avail able for traffic throughout the year. From the Khawak to the head of the Ghorband (a river which meets the Panjshir near Charikar), the Hindu Kush is intersected by passes at intervals, e.g., the Kaoshan (the "Hindu Kush" pass par excellence), 14,34o ft.; the Chahardar (13,90o ft.), on the Afghanistan high road to Turkis tan; and the Shibar (9,80o ft.). Here is the southern extremity of the Hindu Kush, for here commences the Koh-i-Baba system into which the Hindu Kush is merged.
The general structure of the Hindu Kush south of the Khawak, no less than such evidence as at present exists to the north, points to similar conditions of uplift and subsequent denudation as in the western Himalaya and the whole of the trans-Indus border land. The uplift was later than the Himalayas and was marked by the overthrusting of Cretaceous limestones upon Recent shales and clays as on the Baluch frontier. The Hindu Kush is, in fact, but the face of a great plateau-land lying north of it, just as the Himalaya forms the southern face of the table-land of Tibet, and its general physiography, exhibiting long, narrow, lateral valleys and transverse lines of "antecedent" drainage, is similar. There are few passes across the southern section of the Hindu Kush which have not to surmount a succession of crests or ridges as they cross from Afghan Turkistan to Afghanistan. The excep tions are notable, and have played an important part in the mili tary history of Asia. From a little ice-bound lake called Gaz Kul, which lies on the crest of the Hindu Kush near the Taghdumbash Pamir, two very important river systems (those of Chitral and Hunza) are believed to originate. The lake really lies on the water shed and is probably a glacial relic. Its contribution to either stream appears to depend on the blocking of ice masses towards one or other end. It marks the commencement of the water-divide which separates the Gilgit basin from that of the Yashkun, and subsequently divides the drainage of Swat, and Bajour from that of the Chitral (or Kunar). The Yashkun-Chitral-Kunar river is the longest affluent of the Kabul, and it is in many respects a more important river than the Kabul. It is closely flanked on its left bank by this main water-divide. It is this range, crowned by peaks of 22,000 ft. and of an average height of 1 o,000 ft. throughout its length of 250 m., that is the real barrier of the north—not the Hindu Kush itself. Across it are glacial passes (Darkot) which lead to the foot of the Baroghil. Those passes (the Kilik and Mintaka, both above 15,000 f t.) from the Pamir, which lead into the gorges of the upper affluents of the Hunza, east of Darkot, belong rather to the Murtagh system. Other passes are the Shandur (12,250 ft.), between Gilgit and Mastuj ; the Lowarai (10,45o ft.), between the Panjkora and Chitral valleys; and farther south certain lower crossings which formed part of the great highway between Kabul and India.
Facing Chitral, on the right bank of the river, and extending for 7o m., is the lofty snow-clad spur of the Hindu Kush known as Shawal, across which one or two difficult passes lead into the Bashgol valley of Kafiristan. This spur carries the boundary of Afghanistan. South of Arnawai the Kunar valley becomes a part of Afghanistan (see KUNAR) . The value of Chitral as an out post of British India may be best gauged by its geographical po sition. The Durah pass leads into the Chitral valley from the Oxus, as also the Mandal pass, a few miles south, is the connecting link between the Oxus and the Bashgol valley of Kafiristan ; and the Bashgol valley leads directly to the Chitral valley at Arnawai, about so m. below Chitral. Nor must we overlook the connection between north and south afforded by the long narrow valley of the Chitral (or Yashkun) itself, leading up to the Baroghil pass. This route was once made use of by the Chinese for purposes of pil grimage, if not for invasion. Access to Chitral from the north is therefore but a matter of practicable tracks, or passes, in two or three directions, and the measure of practicability under any given conditions can best be reckoned from Chitral itself.
Historical.—Hindu Kush is the Caucasus of Alexander's his torians. It is also included in the Paropamisus, though the latter term embraces more, Caucasus being apparently used only when the alpine barrier is in question. It was no doubt regarded (and perhaps not altogether untruly) as a part of a great alpine zone believed to traverse Asia from west to east, whether called Taurus, Caucasus or Imaus. Arrian himself applies Caucasus dis tinctly to the Himalaya also. The application of the name Tanais to the Syr seems to indicate a real confusion with Colchian Cau casus. Alexander, after building an Alexandria at its foot (probably at Hupian near Charikar), crossed into Bactria, first reaching Drapsaca, or Adrapsa. This has been interpreted as Anderab, in which case he probably crossed the Khawak pass, but the identity is uncertain. The ancient Zend name is, according to Rawlinson, Paresina, the essential part of Paropamisus; this accounts for the great Asiatic Parnassus of Aristotle, and the Pho-lo-sin-a of Hsuan Tsane.
The Hindu Kush, formidable as it seems, and often as it has been the limit between petty states, has hardly ever been the boundary of a considerable power. Greeks, White Huns, Samani dae of Bukhara, Ghaznevides, Mongols, Timur and Timuridae, down to Saddozais and Barakzais, have ruled both sides of this great alpine chain. (See also AFGHANISTAN; INDIA.) publications before 190o the following are very useful:—Report of the Russo-Afghan Boundary Commission (1886) ; Report of Lockhart's Mission (1886) ; Report of Asmar Boundary Commission (1895) ; Report of Pamir Boundary Commission (1896) ; J. Biddulph, Tribes of the Hindu Kush (Calcutta, 188o) ; W. M`Nair, "Visit to Kafiristan," vol. vi. R.G.S. Proc., 1884 ; F. Younghusband, "Journeys on the Pamirs, etc.," vol. xiv. R.G.S. Proc., 1892 ; Colonel Durand, Making a Frontier (London, 1899) ; Sir G. Robertson, Chitral (London, 1899) ; L. M. P. d'Orleans, a travers l'Hindo-Kush (1906) ; L. J. Thomas, Beyond the Khyber Pass (1925) ; E. Suess, The Face of the Earth (Eng. trans., 5 vols., 1904-1924)•