But Chief Biehl defended his approach, saying it allowed the police to focus dwindling resources on serious crimes. Immigrant leaders, especially Hispanics, embraced it, becoming less wary of the police.

“If we have any group of citizens who are afraid to talk to us or don’t trust us,” Chief Biehl said, “that’s going to compromise our ability to produce public safety.”

City officials said the whole effort cost them one salary for a program coordinator and some snacks for meetings. While it is still too early to say whether the program will jump-start an economic rebound, the early results are promising.

Turks chose Dayton, Mr. Shakhbandarov said, because the cost of living was low and there were universities nearby for their children. The newcomers have started restaurants and shops, as well as trucking companies to ferry equipment for a nearby Air Force base. And they have used their savings to refurbish houses in north Dayton, where Turkish leaders estimated that they had invested $30 million so far, including real estate, materials purchases and the value of their labor.

Mr. Shakhbandarov stood proudly at the entrance of the Turkish community center that recently opened downtown, gesturing to the lobby’s beige floor tiles, imported from Turkey to make visitors “feel warm” when they arrive. Turks bought the center, empty and dilapidated, from the city with a favorable loan. Now it houses a neighborhood preschool and martial arts classes, joined enthusiastically by girls in head scarves.

“It’s all about attitude,” Mr. Shakhbandarov said. “Americans maybe have seen better days of Dayton, a better life, better economy. But we never seen that. We have learned to appreciate what we have. And what we have here is much beyond what we ever had before.”

Other immigrants are busy as well. Organized by Migwe Kimemia, a Kenyan immigrant who works for the American Friends Service Committee, a group of Africans is working to start a roasting company in Dayton for coffee from that continent.