Transcript for Major milestone in war against ISIS

Overseas tonight, a major MI milestone in the war against ISIS. The Syrian city, the islamic state calls its capital. But after years of militant control and fierce battle, the devastating toll is very clear tonight. You're about to see it, and as ISIS loses its territory in Syria and Iraq, where does it turn next? Back to the internet? Here's ABC's senior foreign correspondent Ian Pannell tonight. Reporter: Tonight, u.s.-backed forces celebrate a hard-won victory. ISIS fighters now all but driven out from raqqah. These celebrations in the same square where ISIS took over the city three years ago, making it their capital. But look at the ISIS fighters now. Some will be held as specialty foreign fighters, but others will be free to rejoin their families. The U.S. Provided training, weps and aerial support. But it's local people who have done the fighting and dying. We joined them this summer as the battle of raqqah was raging. As they dodged snipers and suicide bombers. These are the fighters that the U.S. Coalition is working with, they are the foot soldiers moving to their forward base. Now, women allowed to show their faces on the streets for the first time in years. But the destruction is so vast, it will take years to rebuild. And more than 6,000 ISIS militants are still out there, ready to go underground, regroup, fight and die. The celebration is hard-fought, but the group remains a potent force underground. And the ISIS leader already threatening attacks in America, Europe and Russia.

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