BARKSDALE AIR FORCE BASE, La.-- -- With the roaring arrival of 12 F-15E Strike Eagles of the 389th Fighter Squadron from Mountain Home Air Force Base, Idaho, their equipment and maintenance crew, exercise Green Flag East officially starts on Barksdale.

The empty halls at the 548th Combat Training Squadron are now filled with the hustle and bustle of a unit about to deploy.

Working closely with the U.S. Army at Fort Polk, the F-15s are here to learn to respond to and support ground forces with close air support which is defined by air actions by fixed or rotary winged aircraft against hostile forces in close contact with friendly forces.

"In a nutshell, what we're here to do is integrate with the Army by providing CAS," said Maj. Paul Siegler, F-15E Strike Eagle pilot. "By working with the Army prior to deploying, we can familiarize ourselves with Army procedure and doctrine to be much more effective when we're down range."

As flying operations start, there are many briefings and classes held to inform aircrew on their objectives and who they will be working with at Fort Polk. The first lesson is on CAS, Emergency Close Air Support and FIRES.

"The first academics class is a refresher course on CAS, going over the basics and defining what it is," said Lt. Col Brett Waring, 548th CTS Det 1 director of operations. "The difference between CAS and ECAS, put in layman's terms, is CAS is called in by a Joint Terminal Attack Controller to strike the enemy, and ECAS is calling in CAS without a JTAC, and FIRES is the use of weapon systems to create lethal or non-lethal effects upon hostile forces. All of this is to reinforce what is already known about CAS and introduce new procedures learned over the past decade in Afghanistan and Iraq."

Once the unit arrives in theater, aircraft are assigned to certain Army units and areas to cover. Some areas receive more coverage than others depending on enemy activity in the area and what the unit on the ground is there to do.

"Down range, there is pre-planned CAS where Army commanders will split up aircraft to cover certain units depending on location and activity in that area, and will regularly patrol the airspace and provide support," said Sieger. "For unplanned CAS missions, also known as ECAS, there are aircraft on alert that can be ready within 15 or 30 minutes depending on the activity in their area. ECAS is called in when "Troops-in-Contact" is declared, say a convoy is under attack, and a request for immediate air support is needed. Nearby aircraft will respond and work with JTACs to pinpoint where friendly positions are and where the enemy is to support the TIC."

Like the old saying "train as we fight, fight as we train", GFE serves to reinforce the combat skills of both services.

"In a sense, the Air Force and Army speak different languages and there will always be difficulty in working together, but attending GFE helps both services to remain combat ready as well as foster inter-service relations," Sieger said.