Where the Islamic State ruled in Syria, fear and uncertainty reign

MANBIJ, Syria — Cities and towns across eastern Syria are overwhelmed by rubble. The militias that fought the Islamic State group are digging tunnels to prepare for a possible battle against Turkey. A recent explosion in the city of Raqqa killed nine people.

The routing of the Islamic State from its final piece of territory in Syria last month was hailed as a milestone in the fight against the world’s most fearsome terrorist organization. But the territory it once ruled remains in shambles, insecure and its future uncertain.

Entire communities are destroyed, with little help to rebuild. A range of powers — the Syrian government, Turkey, Russia and militias backed by Iran — hope to fill the void left by the jihadis’ defeat. And the Islamic State is not even gone: While the bombings that killed at least 250 people in Sri Lanka last week demonstrated that its ideology continues to echo globally, in Syria thousands of its fighters have merely gone underground to launch attacks and plot their comeback.

“We are talking about a secret organization that is still operating,” said Redur Xelil, a senior official with the Syrian Democratic Forces, the Kurdish-led militia that the United States backed to fight the jihadis. “It has a network, means of communication and a central command.”

A Kurdish-led administration is struggling to govern the area, which encompasses roughly the third of Syria east of the Euphrates River. But the United States, which led the military coalition to defeat the Islamic State, has not recognized the local administration and will not help with reconstruction.

Having won the war, the United States risks losing the peace.

The United States remains the area’s de facto protector, its 2,000 troops presumed to be the only barrier deterring incursions by Russian, Turkish or Syrian...