Iraqi government forces are putting the squeeze on the Islamic State of Iraq and Syria to reclaim the northern city of Tikrit, an ISIS stronghold 80 miles north of Baghdad.

Iraqi forces took back a town on the outskirts of Tikrit, according to their commanders. The battle for the strategically key city is in its sixth day.

Iranian-backed militias are beefing up the Iraqi offensive, which is earning praise from the Obama administration.

Army Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, told reporters Saturday morning that he's optimistic the Iraqi government will prevail.

This is the biggest offensive against ISIS since the militants swept across Iraq last year. Officials in Iraq said nearly 30,000 men are fighting the extremists.

The fierce fighting has forced thousands to be evacuated. CBS News' Holly Williams spoke to one family.

Raad Saleh Ateia and his wife, Quraish, fled their home in Tikrit just three days after ISIS captured the city in June.

"Armed men from ISIS took our son Omar away," Quraish told CBS News. "I chased after the car, and I was crying because I couldn't keep up."

Raad told CBS News that ISIS interrogated 20-year-old Omar and accused him of drinking alcohol.

The militants later released him, but Omar is still too frightened of ISIS to appear on camera.

In its violent propaganda videos, ISIS glorifies its brutal executions of Americans, Christians and others they consider to be non-Muslims.

But the truth is that ISIS has killed and terrorized more Muslims than it has members of any other religious group.

Quraish is optimistic that Iraq will be free of ISIS.

"Yes, God willing," she told CBS News. "We hope Iraq will be free and everyone can go home to their families."

If Iraqi forces can retake Tikrit, many there believe the next target will be Mosul, the country's second-biggest city.