As CBS News senior national security correspondent David Martin reported on Thursday, President Trump appears to be standing firm on his decision to pull American forces out of Syria. The president himself has not yet commented on the topic since four Americans were killed in a targeted attack by ISIS in northern Syria on Wednesday. But Vice President Mike Pence did reiterate Mr. Trump's assertions, not long after the U.S. confirmed the casualties, that ISIS had been defeated in Syria and it is time to bring American troops home.

Visiting the front lines of the ongoing war this week with U.S.-backed Kurdish fighters, however, CBS News correspondent Charlie D'Agata saw a different reality. What follows is his report from the front-line town of Ash Sha'fah, in eastern Syria.

Ash Sha'fah, Syria -- President Trump and Vice President Pence may continue to insist that ISIS is defeated in Syria, but the frontlines here tell a very different story, with U.S. forces and their allies on the ground battling a persistent enemy that refuses to surrender.

Even as we made our way toward the fighting, we were warned that ISIS terror cells lurked among the ruined villages, launching counterattacks and planting bombs on the only road in and out.

We travelled to the front lines in eastern Syria, the very last pockets of ISIS resistance. Once these areas are taken back, ISIS will not be considered a territorial force here.

We arrived in Ash Sha'fah to see Kurdish-led forces firing a barrage of mortars toward ISIS positions not much more than a mile away.

Nearby, vital reinforcements: U.S. troops and military hardware. An American position is just a few hundred yards away from the Kurdish forces we're embedded with. The U.S. forces have been firing mortars in the direction of the ISIS holdouts since we got here.

"They're playing a very big role," Kurdish commander Simko Shkak told us. "Their forces have been very effective. We give them coordinates for ISIS locations and their Air Force and artillery do all they can."

In addition to roughly 2,000 U.S. ground forces here, the American-led air campaign has been pummelling this territory, carrying out airstrikes on 1,100 targets in the first two weeks of January alone. The missiles have focused on the sliver of land still under ISIS control.

Commanders here tell us the final push could take a month or more. But as the tragic deaths of four Americans among more than a dozen killed in the Manbij attack on Wednesday shows, ISIS is already morphing into an insurgency that has begun striking targets far beyond these battlefields.