"Hamas, to my great regret, is Israel's creation," says Mr. Cohen, a Tunisian-born Jew who worked in Gaza for more than two decades. Responsible for religious affairs in the region until 1994, Mr. Cohen watched the Islamist movement take shape, muscle aside secular Palestinian rivals and then morph into what is today Hamas, a militant group that is sworn to Israel's destruction.
Instead of trying to curb Gaza's Islamists from the outset, says Mr. Cohen, Israel for years tolerated and, in some cases, encouraged them as a counterweight to the secular nationalists of the Palestine Liberation Organization and its dominant faction, Yasser Arafat's Fatah. Israel cooperated with a crippled, half-blind cleric named Sheikh Ahmed Yassin, even as he was laying the foundations for what would become Hamas. Sheikh Yassin continues to inspire militants today; during the recent war in Gaza, Hamas fighters confronted Israeli troops with "Yassins," primitive rocket-propelled grenades named in honor of the cleric.