ERBIL, Iraq -- ISIS released a video purporting to show a dead hit by a drone on an Iraqi armored personnel carrier. But that did not stop Iraqi forces in their battle to retake Mosul.

They seized control of Mosul’s airport and entered the western half of the city, having already liberated the eastern half.

After Mosul, the next major objective in the war against ISIS is across the border in Syria.

Syrians training to fight ISIS CBS News

CBS News got a look inside an American special operations base in Syria which serves as a hub for the campaign to liberate the ISIS capital of Raqqa.

Syrian fighters training there are part of a force of about 15,000 being assembled to assault Raqqa.

Gen. Joseph Votel CBS News

But Gen. Joseph Votel, commander of U.S. forces in the Middle East, told CBS News they need more than the AK-47s they will be issued after 20 days of training.

“Anti-tank weapons systems to address the vehicle-born IEDs. Certainly mortars would be something of help,” Votel said. “Things that they would need of a force that’s going to conduct an assault.”

The weapons would be flown into a dirt airstrip built for the U.S. by a Syrian engineer who lost his family to ISIS.

The plane carrying news crews to the base was a tilt-rotor Osprey aircraft, but the strip is long enough to handle large cargo planes from the United States.

Lt. Gen. Steve Townsend, the commander of the campaign both Iraq and Syria, says what’s at stake is heading off terrorist attacks in the works.

“There are threat streams that are external-operations focused emanating from Raqqa right now. Most of them point, quite honestly, at Europe,” he said.

One American officer said he expects the Syrian fighters to suffer heavy losses in the battle for Raqqa.

And this is no-prisoners fighting on both sides; According to U.S. estimates, 1,600 ISIS fighters have been killed in the last four months in Syria and only a dozen wounded.