HABUR BORDER GATE, Turkey — In normal times, hauling 50,000 pounds of frozen chicken into Iraq is a routine job for Turfan Aydin, a Turkish trucker who has been working the route for years. But the cross-border trade has suddenly all but halted, locked up by the insurgent offensive in Iraq and the kidnapping of 80 Turkish citizens.
Once this border was wide open, as Turkey allowed rebel groups of any stripe easy access to the battlefields in Syria in an effort to topple President Bashar al-Assad. But that created fertile ground in Syria for the development of the Sunni militant group that launched a blitzkrieg in Iraq this month, the Islamic State in Iraq and Syria.
“For three years, we have seen ISIS flags in Syria, and that is because of Turkey,” Mr. Aydin said, eyeing hundreds of Iraq-bound trucks that snaked in a line over the horizon. “Turkey let them in.”
“The fall of Mosul was the epitome of the failure of Turkish foreign policy over the last four years,” said Soli Ozel, a professor of international relations at Kadir Has University in Istanbul. “I can’t disassociate what happened in Mosul from what happened in Syria, and Turkish foreign policy toward Syria has been unrealistic, hubristic, ideological and stubborn.”
For years, a “zero problems with neighbors” policy helped make Turkey a much-admired example of Islamic democracy and economic growth. It benefited heavily from the opening of Iraq’s market, exporting $12 billion worth of goods last year, second only to Turkey’s exports to Germany. That number could drop by one-quarter, or even more if the fighting spreads, said Atilla Yesilada, a Turkey analyst at GlobalSource Partners.
These losses came after the civil war in Syria destroyed that country’s ability to buy Turkish goods and sent hundreds of thousands of refugees streaming across the border. Turkey has spent $1.5 billion caring for them, with no end in sight.
The new strife in Iraq is just another in a series of domestic and foreign policy setbacks for Prime Minister Recep Tayyip Erdogan and his ruling Justice and Development Party.
The brilliant success Mr. Erdogan enjoyed for years after coming to power more than a decade ago has been tarnished recently by street protests, a devastating mine disaster and a lengthy corruption scandal. The government’s support for Arab uprisings further isolated it from former allies.
Many here are now blaming the Turkish government for facilitating the rise of extremists in Syria.
Turkish leaders have expressed concern about the rise of jihadists near their borders, and say they have stepped up efforts to track extremists. But they have said little about the militant surge in Iraq, and a spokesman for the Foreign Ministry declined to comment on how it would affect Turkish policy.
Lately, however, Ankara has given some indications that it is adjusting to the shifts in its region.
This month, it classified the Nusra Front, Al Qaeda’s Syrian affiliate, as a terrorist organization — a year and half after the United States did so. In Ankara on Tuesday, Mr. Erdogan called on European nations to stop jihadis from traveling to Turkey. And Turkish officials have remained quiet about the takeover of the Iraqi city of Kirkuk by the forces of the Kurdistan Regional Government, a show of assertiveness that would have prompted instant condemnation a few years ago.
That silence could mean that Turkey sees Iraq’s Kurds as the only reliable partners in a country on the edge of a new civil war between Sunnis and Shiites, said Sinan Ulgen, a Turkey scholar with the Carnegie Endowment for International Peace in Brussels.
The hardest blow from Iraq’s new strife, however, has hit Turkey’s southeastern corner, which gained the most from the expanded trade with Iraq and has the most to lose if it collapses.
This change is clear at the Habur Border Gate, which just weeks ago channeled more than 2,000 trucks of Turkish goods into Iraq each day. Now, fewer than half that number make the trip because of a drop in demand and the risk of transporting goods.
Highlighting that danger is the plight of about 80 Turkish citizens who were kidnapped by ISIS when it seized Mosul. They include the consul general, three children and 31 truck drivers. None have been seen since.
The kidnappings have terrified communities that rely on cross-border trade. Doruklu, a village of 1,300 people where some residents still live in mud-brick homes and most men become truckers as soon as they reach adulthood, counts four men among the captive truckers.
“This is all we talk about day and night, but there is nothing we can do,” said Mehmet Turgut, who leads prayer in the village mosque.
Nearby, Nihal Simsek, whose husband and eldest son are being held by ISIS, showed a framed photo of the two men to visitors to her simple concrete-block home, then collapsed on the porch, hugging the photo as tears dripped from her chin.
“They just went to bring back money, just to make a living,” she said. “We can live without money, but we can’t live without them.”
The truckers have managed to keep a few cellphones hidden and occasionally call to reassure their relatives, their families said. They are being fed and say they have not been mistreated, though they have no idea when they will be released.
Mehmet Kizil, who owns the company the truckers work for, said that ISIS members first demanded $5 million to $10 million for the men’s release, but that he had not been involved since the government took over the negotiations.
Turkish officials have said they are working to release the captives but have also banned the news media from reporting on the issue.
The danger still has not dissuaded most truckers from going to Iraq, as was clear from the long line of rigs waiting for their turn. Many truckers had waited in line for more than 24 hours, passing the time listening to music, playing games on their phones, making tea on small gas stoves and sleeping.
“If things were functioning the way they were supposed to, you couldn’t even stand here and talk,” said Abdul Hafur, a gray-haired trucker who said it had taken him a week of calling to find a load to take into Iraq.
Like many of his colleagues, he had gone into deep debt to buy his truck and now feared he would fall short on his payments. To shore up the family’s finances, he had sent three of his children to work picking tomatoes and cleaning rooms in a tourist hotel, he said.
Nearby, Mr. Aydin, whose truck held the frozen chicken, said he owed $47,000 on his truck and had to pay $2,700 a month. But business had slowed so much he was unsure he would earn enough to pay.
“We have to go to Iraq,” he said. “We have no other choice.”