In 1964, Israel hijacked the waters of the River Jordan. The Jordan Valley, a green desert strip that had been cultivated for longer than perhaps anywhere else on Earth, was overnight deprived of most of its water. One day the River Jordan poured out of Golan Heights, into the Sea of Galilee and on down the valley to the Dead Sea. The next day, an Israeli dam blocked the river's outflow from the Sea of Galilee. Instead, a pumping station lifted the water out of the sea and into a 10-foot-wide pipeline that delivered it along the length of Israel.

Almost three years after Israel grabbed the waters of the Jordan, it fought the Six Day War with its Arab neighbors. Most histories of the war discuss its causes in terms of land and security. They often ignore water. Yet the simple fact is this: Prior to the 1967 war, less than a tenth of the River Jordan's basin was within Israeli borders; by the end, it was almost entirely controlled by Israel.

A happy chance? Some say so. But in his autobiography, Ariel Sharon, who was a commander in the Six Day War and much later became prime minister, was unabashed about the hydrological motives of Israel in that conflict, though he said the other side started it. In the early 1960s, he wrote, Syria committed the first offensive act on the River Jordan by starting to dig a canal in the Golan Heights to divert the Jordan's headwaters away from Israel. "The Six Day War really started on the day Israel decided to act against the diversion of the Jordan," he wrote.

The war was, by this account, the first modern water war. And Israel's victory in seizing the River Jordan and its catchment remains an essential backdrop to today's continuing conflicts. This article is excerpted from the author's book When the Rivers Run Dry, with the permission of its publisher, Beacon Press, Boston. Copyright © 2006 by Fred Pearce.