For two thousand years, the closer to Carthage (roughly the site of modern-day Tunis) the greater the level of development. Because urbanization in Tunisia started two millennia ago, tribal identity based on nomadism--which the medieval historian Ibn Khaldun said disrupted political stability--is correspondingly weak. Indeed, after the Roman general Scipio defeated Hannibal in 202 B.C. outside Tunis, he dug a demarcation ditch, or fossa regia, that marked the extent of civilized territory. The fossa regia remains relevant to the current Middle East crisis. Still visible in places, it runs from Tabarka on Tunisia's northwestern coast southward, and turns directly eastward to Sfax, another Mediterranean port. The