Transcript for Syrian forces battle ISIS for the city of Raqqa

We move on to the fight against ISIS and the battle to take back a key city in Syria under its control. Raqqah became the effective ISIS capital in 2014. Now, Syrian forces are moving in and ABC's Ian Pannell has gone deeper into raqqah and the battle against ISIS than any other U.S. Broadcaster and he joins us from that region. Good morning, Ian. Reporter: Robin, with mosul pretty much done raqqah and Syria is where ISIS is making its last stand. Don't underestimate how important this is. We're talking the capital of ISIS and the outcome matters to America, Europe and the people who live here. Raqqah, Syria, ground zero in the war against ISIS, with u.s.-backed forces locked in a fight to the death. ISIS snipers who killed many here are moving quickly, the only option. We moved up to the front line with local fighters. The going is as slow as it is dangerous. You can hear the battle for raqqah is ongoing. You've got local forces backed by the United States taking the battle to them. Sounds of gunfire and drones overhead and coalition air strikes every few minutes and here we met an American sniper on the front line. A young volunteer from California. If a member of ISIS was in this room right now with all of us, what chance would he give you or you or me? None. No part of you that's scared, nervous, anxious at this point? No, not really. I came here for this, you know. I've been waiting for years for this. This is the final stand-up fight between us and them. After them, you know, that's it. Reporter: For many this is a calling. A chance to reclaim the streets from ISIS for good. That's enough for today. Reporter: Privately coalition commanders admit this battle could drag on for months. No doubt local forces are committed but underequipped to fight ISIS and as we saw last week America's allies are suffering heavy casualties. You can see more of Ian's front line reporting on abcnews.com and "World news tonight" with David Muir. New details about that human

This transcript has been automatically generated and may not be 100% accurate.