ERBIL, Iraq -- The U.S. airstrikes in Iraq that began a month ago saved thousands of refugees trapped by the Islamic State of Iraq and Syria militant group on Mount Sinjar and stopped the ISIS advance on the Kurdish capital of Erbil.

Kurdistan is a semi-independent region in northern Iraq with its own military called the Peshmerga. Scott Pelley, reporting there for "60 Minutes," found them Wednesday eye to eye with ISIS.

The ISIS advance stopped just short of Lieutenant Mohammad's bridge. The ISIS flag can be seen on one end of the bridge and Mohammad's men on the other.

"This is the road to Kirkuk," Mohammad said.

Kirkuk is the gateway to Iraq's oil fields. Mohammed said he does not have orders to destroy the bridge because "the people will need the bridge, no one's going to take my bridge."

He couldn't have said that a month ago when these troops were forced back towards the capital, Erbil. But now, the American air campaign means ISIS can't mass its forces or move with any speed.

Thanks to the U.S. airstrikes, the Peshmerga are now on the offensive and eventually the Peshmerga will be moving toward Mosul which is an occupied city of more than a million and a half people.

Images coming out of Mosul show its chaos, according to a doctor who moves in and out of the city. CBS News won't identify him, for his safety.

"Mosul is like a big prison with limited water and gas," he said. "Electricity only shows up once every two days. The people have no work. There is a massive shortage of medicine."

The doctor said people in Mosul today must abide by strict rules to live under ISIS.

"They control life, clothing, everything in a very harsh way, very strict and very strict punishments," he said.

ISIS is posting those punishments online, boasting of mass executions of people who refuse to convert to its extremist view of Islam.

A man named Sayid told CBS News that last month ISIS rounded up more than 100 men in his village and told them they were being taken to a refugee camp. It turned out to be a short trip to a mass grave.

Sayid told CBS News that he survived a mass execution carried out by ISIS. CBS

"They told us to lie flat on the ground," Sayid said. "Then they started firing all kinds of guns."

His leg was hit three times; a bullet grazed his neck.

"When I was hit, I didn't want to make a sound because anyone who made a noise, they'd come over and shoot them in the head," he said.

When it was all over, Sayid crawled out of the grave.

Back at the bridge, Lieutenant Mohammad's men can't advance because his men are lightly armed. The Kurds are asking the White House for tanks and artillery, to break lines like this. It could be a long commitment. War is like a bridge - once you're on it, you can't get off until you see it through.