Jerusalem first enters written history as one of the towns of which the rulers were in correspondence with Egypt in the period covered by the Arnarna letters, in the first third of the 14th century B.C. It later appears in the Book of Joshua as a town of the Jebusites (a Canaanite tribe) who dwelt in the midst of the Israelites and were not conquered by them in the earlier stages of the entry into Palestine. It thus enters the historical stage as an important Canaanite town of the second half of the second millennium B.C. Its importance lies in its position. The physical configuration of Palestine with its north-south division of, from west to east, coastal plain—upland ridge—Jordan and Dead Sea Valley—plateau of Transjordan, means that a town dominating the backbone of the upland ridge is of major political importance, particularly when the coastal plain was under the control of alien powers, for the Jordan Valley route is not an important throughroute, owing to the spread of the Dead Sea from cliff to cliff of the valley. For most of the second millennium Egypt controlled the coastal plain, and from about 1200 B.C. onwards it was under Philistine domination. Jerusalem lies athwart the backbone of the upland ridge at a point where it is intersected by an important east-west route. The control of Jerusalem was therefore essential to the development of the political power of the Hebrews, who had infiltrated into Palestine in the second half of the second millennium B.C. Only when Jerusalem was captured by David about 995 B.C. could the Hebrew groups be combined into a nation.