By Liz Sly October 30 at 4:12 PM

A cage in which Islamic State militants temporarily held people caught smoking while the militants held control of Tal Abyad, in Raqqa province. (Alice Martins/For The Washington Post)

TAL ABYAD, Syria — When Islamic State fighters fled this northern Syrian town in June, they took with them the electricity generators, the water pumps, the hospital equipment and pretty much everything else that had helped sustain the semblance that they ran a functioning state.

They left behind their graffiti, their instruments of torture, the block of wood on which they beheaded their victims, the cage in which they punished smokers — and a community riven with suspicion and distrust.

Today, Tal Abyad is a tense and troubled place. Its new Kurdish masters are seeking to assert their control over a mixed town that, at least until recently, had an Arab majority — some of whom were not entirely unhappy to be governed by the Islamic State.

“As long as you didn’t bother them, they didn’t bother you,” said Sarkis Kaorkian, 60, who is one of the town’s few Christians who remained behind and is now deeply relieved the Islamic State is gone. He claims he drank and smoked his way through the group’s 17-month rule by staying out of their way and paying on time the $100 tax, or jizya, leveled twice a year on Christian residents.

These days, Islamic State sympathies abound among local Arabs in the town, say residents who close up their shops by nightfall, just in case. The assassination of a local imam outside his mosque this month reinforced their concerns.

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Occasional suicide bombings keep Tal Abyad on edge, and recent attacks by Turkey underscore the kind of complications likely to arise as the U.S.-led effort to defeat the Islamic State liberates territory in Iraq and Syria — absent a wider settlement to the many rivalries fueling the region’s wars.

As the U.S. military prepares to deploy 50 Special Operations troops to the vicinity ahead of a new focus on the Islamic State’s self-styled capital of Raqqa, 60 miles to the south, Tal Abyad represents something of a test also for a strategy that will rely heavily on the Kurdish People’s Protection Units, or YPG, to take control of Arab areas.

Located on Syria’s border with Turkey, Tal Abyad is among the most strategically significant of the conquests made under the umbrella of the 14-month-old U.S. air campaign against the militants. The trading town had served as the Islamic State’s main gateway to the outside world, the transit point for foreign fighters arriving to join the group and for supplies of everything from Nutella to the fertilizers needed for making explosives.

Its fall within two days to the YPG represented a major defeat for the militants and has been held out by the U.S. military as a blueprint for future battles involving capable ground forces backed by U.S. airstrikes. The collapse followed two weeks of intense airstrikes against Islamic State positions in villages surrounding the town, and the group’s fighters appear to have chosen to flee rather than fight.

It was also, however, a significant setback for Turkey, which has vowed to prevent the establishment of a Kurdish region along its southern border with Syria. Turkey accuses the YPG of ties to Turkey’s domestic Kurdish separatist movement, the Kurdistan Workers’ Party, or PKK, which is designated a terrorist organization by Ankara and Washington.

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Turkish soldiers on the other side of the heavily reinforced line opened fire this week on Kurdish positions in Tal Abyad on at least one occasion, a measure of the determination of Turkish President Recep Tayyip Erdogan “to do whatever is necessary” to push back against the Kurds’ expanding presence in Syria, as he put it earlier this month.

The border crossing, once one of the busiest between Turkey and Syria, has been sealed shut for months, hampering deliveries of food and humanitarian aid and further undermining Tal Abyad’s recovery.

It is against this backdrop that the Kurdish YPG has set about absorbing Tal Abyad into its self-declared Kurdish autonomous region, which now stretches more than 300 miles from the Iraqi border in the east to the banks of the Euphrates River in the west.