EBEL EL SAQI, Lebanon — The peacekeepers passed scorched fields and bombed houses and hollowed-out towns, the landscape of southern Lebanon’s stop-and-start war.

       On the road, in white armored vehicles waving the blue flag of the United Nations, they encountered people who could not leave the conflict zone, who refused to go or were paid to stay: Lebanese soldiers, Syrian farmhands, a cafe owner thrilled to see them and other residents who barely seemed to notice them.