DIYARBAKIR, Turkey — Across the Kurdish lands of southeast Turkey, a bitter war that had long been stilled by a truce has suddenly come roaring back, threatening to undo a hard-won economic turnaround here and adding a new battlefield to a region already consumed by chaos.

Cafes in this city that usually stay open until midnight now close at dusk. Jails are filling, once again, with Kurdish activists and officials accused of supporting terrorism. Residents say they are stocking up on weapons, just in case.

In the mountains, Kurdish guerrillas hastily set up vehicle checkpoints and then dissolve into the rugged terrain in a game of cat and mouse with Turkish soldiers. In the countryside, burned and mangled vehicles blight a landscape blackened by forest fires set by the Turkish Army — a tactic that destroys militant hide-outs but also apple and cherry orchards and stocks of feed for villagers’ cows and goats.

“It shouldn’t be like this,” said Kudbettin Ersoy, 66, who sells watermelons here from a wooden cart. “I was hopeful that peace would come and the blood would stop flowing. We are all citizens of this country.”