The U.S. military acknowledged today that it had begun bombing ISIS, the Islamic militant group, in an effort to stave off its encroachment into northern Iraq.

FRONTLINE producer Martin Smith just returned from a trip near Mosul, about 20 miles from where American warplanes targeted ISIS positions earlier today. There, Smith visited a U.N.-run camp for displaced Iraqis who had fled the city as the militants moved in. Taxi drivers, tailors, construction workers, who huddled in sweltering tents, told stories of the brutality of ISIS. They had nowhere else to go. And their only defense: a large trench dug around the camp.

Smith, now back in Baghdad, spoke to Marco Werman at PRI’s The World this afternoon about what he’s seeing on the ground. Listen to the interview below:

FRONTLINE producer Martin Smith (Gangs of Iraq, Private Warriors, Beyond Baghdad, Truth War and Consequences) is in Baghdad, working on a film about Iraq’s current crisis with cameraman Scott Anger and second camera/soundwoman Sachi Cunningham. Read Smith’s dispatches on his return to Baghdad and the city’s checkpoint problem.