When Menachem Begin returned the Sinai peninsula to Egypt in 1982, Israel thought it was getting not only peace but, in exchange, a buffer zone that would protect it from a hitherto intractable foe. The northern coastal plain connecting Africa to Asia was too scrubby to sustain much life. Its largest town and provincial capital was called El Arish, Arabic for palm huts. Arid inhospitable mountains dominated the center and south. And the Camp David Accords that Egypt and Israel signed in 1978 required Egypt to keep its soldiers and tanks away from the Sinai; the eastern half was turned into a demilitarized zone monitored by a US-dominated multinational force. (See the map below.)

All that is changing as new forces pile in. Egypt has a new ruling party that sees Israel more as a threat than an ally. Tellingly, President Mohamed Morsi chose to visit Sinai on the eve of the anniversary of the 1973 war that Egypt fought to regain the peninsula from Israel. In Gaza, to Sinai’s northeast, a new power—the Palestinian Islamist movement Hamas—has emerged with a military force and economic power able to project its influence into Sinai, with which it shares ancient tribal and cultural ties. Above all, rapid population growth has turned Sinai’s indigenous population of Bedouin people into a power to contend with, particularly in the corner of North Sinai where Egypt, Israel, and Gaza meet.

The Bedouin people are descendants of the nomads who crossed the Red Sea from the Arabian Peninsula between the fourteenth and eighteenth centuries. They consider themselves Egypt’s only real Arabs, and view other Egyptians as Arabized Africans. Their numbers have grown eightfold in forty years; today, several of their twenty tribes are tens of thousands strong. And though many are moving to new sprawling cities like El Arish, the tribes have established separate suburbs and have yet to settle down. To dilute their growth, Cairo’s leaders have relocated hundreds of thousands of Egyptians to Sinai from the Nile Valley, with their different Arabic dialect, culture, and historical background. The newcomers administer the territory, exploit its raw materials, and run a southern Riviera along its coasts at towns like El Arish, where over three million tourists are expected each year.

Ostracized by the Mubarak regime, which viewed them as a potential fifth column and denied them a share of the tourism industry on Sinai’s coast, Sinai’s Bedouin tapped other sources of finance and support. To the north, they found a ready partner in Hamas, which was under siege by Israel and anxious to find alternative supplies of food, fuel, and sometimes arms. Together, Sinai’s Bedouin and Hamas dug—sometimes with Egyptian government collusion—hundreds of tunnels under their common border. Their cross-border clan networks, intimate knowledge of the terrain—“I can…