Inside the US Command Center at the Front Lines of ISIS Fight

— -- On the same day the Pentagon said it’s considering loosening the rules of engagement for striking ISIS targets in Iraq and Syria, ABC News was granted rare access to a military command center in Northern Iraq, where US and Kurdish officers are making those day-to-day, life and death decisions.

ABC News’ Martha Raddatz was at the Combined Joint Operations Center (CJOC) in Erbil, Iraq today, a heavily classified setting where teams of military personnel, including Joint Tactical Air Controllers, also known as “strike officers,” are monitoring real-time targets and drone feeds broadcast on screens throughout the room.

The command center operates 24 hours a day coordinating coalition airstrikes against ISIS in northern Iraq. It played a key role in the airstrikes that supported the recent Kurdish offensive that retook the town of Sinjar from ISIS fighters.

A senior American official said every air strike, whether conducted by a fighter jet or unmanned aerial vehicle, night or day, must be cleared by an American general officer. In order to strike a building it has to be determined that it is “sole use ISIS,” meaning there must be certainty that the enemy is not co-mingling there with civilians. “We aim for zero collateral damage,” said one young officer in the CJOC.

The officers in the fight there told ABC News the current rules of engagement suffice and that they “have not hurt our ability to strike ISIS,” as one official put it.

But under pressure to punish ISIS in the wake of the deadly Paris attacks, Secretary of Defense Ash Carter suggested today in an interview with NBC that he is “prepared” to relax those rules of engagement for the air war.

A Pentagon official said Monday’s strikes on ISIS oil tankers, transported by civilian drivers, was the first evidence of that shift. Before destroying hundreds of trucks, the coalition dropped flyers warning the drivers to leave their vehicles.

It’s not entirely clear what else the Secretary may have in mind when it comes to changing these rules. Officials at the CJOC said most of the strikes they are conducting are “dynamic,” meaning they are not pre-planned.

As for progress in the overall fight, one senior official there said ISIS, which he believes is operating more and more like a traditional state, is shifting to a defensive stance, initiating less contact and concentrating on protecting its own troops and the population it is controlling.