A detachment from the 26th Marine Expeditionary Unit has set up a secret firebase in northern Iraq to support operations of the U.S. and coalition forces fighting ISIS.

On Saturday, ISIS targeted the firebase, firing two rockets, one of which landed inside the base, killing one Marine and wounding several others.

Initially, the Pentagon claimed that the Marine, Staff Sgt. Louis F. Cardin, of Temecula, California, was killed by "indirect fire" from ISIS.  But it seems clear that ISIS saw the Marines moving into the firebase and fired directly into the base.

The existence of a combat unit in Iraq that could be targeted by ISIS was unknown until the rocket attack.  The Pentagon claims it was going to announce the existence of the base sometime this week.

CNN:

The Pentagon has yet to formally acknowledge it has established its first U.S. fire base in Iraq in the current fight against ISIS for what the official said will eventually be a limited ground combat operation in support of the Iraqis.

The Marines will be using their field artillery guns in the coming weeks to help defend Iraqi troops as they move towards Mosul. For now, the artillery is to defend another nearby base where American troops are getting 5,000 Iraqi forces ready for the operation to retake Mosul.

The Marines first began moving into the area just two weeks ago from their own base of operations aboard an amphibious assault ship the USS Kearsarge, the defense official told CNN.

The Marines had finished setting up and testing their artillery just two or three days before the attack. There was a brief mention of a coalition fire base in a statement Saturday announcing the death of the Marine, but the official said the only troops there are American Marines and no other coalition forces.

On Sunday, the coalition announced that in consultation with the government of Iraq, the U.S. "has assigned a detachment of U.S. Marines from the 26th Marine Expeditionary Unit to the support of Iraqi Security Force and Coalition ground operations. The detachment from the 26th MEU will add to the Marines and Sailors currently in Iraq" supporting the effort against ISIS.

The Marines have already named the location "Fire Base Bell." The U.S has similar artillery at two other large Iraqi bases, but Bell is the only known fire base. That terminology signifies this is a small remote location designed to use its artillery to support infantry troops at forward locations.

Why the secrecy?  Probably because President Obama had assured the American people many times previously that there would be no combat troops deployed to Iraq.

Of course, this puts a great big bulls-eye on the backs of those Marines, billeting them out in the middle of nowhere, making them highly vulnerable to ISIS artillery and rocket attacks.

It's one thing to have special operators assisting the Iraqis with training, lasing targets for U.S. warplanes, or assassinating high-value ISIS targets.

But Marines are lethal weapons.  They are there to kill ISIS fighters, and the fact that we are using one of our crack Marine outfits as part of this deployment changes the character of our intervention in Iraq.