In Iraq, the two Pioneer squadrons leapfrogged each other during the march on Baghdad, so that one unit was always getting UAVs into the air at any one time. They managed to keep at least one Pioneer out in front of the Marines at all times. The Pioneer can use either a day or a night camera (the max payload is sixty pounds), and was used mainly to spot enemy artillery or armored vehicles. There were some problems with other electronic equipment in the area stepping on frequencies the Pioneer used, which is becoming a more frequent problem as more and more electronic gear is out there broadcasting.
The Pioneer was used a lot in the 1991 Gulf War, and was the experienced veteran among UAVs in 2003. Oddly enough, many of the new UAVs did not do so well. The Marine Dragon Eye short range UAV did less well. The main problem was that the laptop computer used to control it failed after a week and they couldn't get it fixed. For the week the Dragon Eye was in use, it did good work, although the troops had some complaints. First, they thought the UAV was too flimsy, and it's flight time too short (one hour, two would have been much better.) Moreover, the large rubber bands used to launch it kept breaking. And there were problems getting the special batteries used. There should have been a rechargeable battery, or a more common one. The ten kilometer range was also too short, 20 kilometer would have made a big difference. Being able to fly the UAV at a lower altitude (like a hundred feet) would have also helped.
The Predator and Global Hawk, the stars of the Afghanistan campaign, were also present over Iraq and continued to do an excellent job.
The U.S. Army also had some new UAVs for brigades, but it turned out that there were lots of helicopters available and these were preferred over the UAVs.
The main lesson to be learned here is that the UAVs that were found to be most valuable were the ones that did things no other aircraft or spy satellite can do. This means either the "high persistence" (in the air for 12 hours or more) birds (like Predator, Global Hawk and the Marine Pioneer's working in shifts) or the tiny ones (like Dragon Eye) that gave battalion (or even company) commanders their own aerial recon capability. But the little ones like Dragon Eye have to be more rugged.
The U.S. Marines typically get a lot of hand me down equipment, and this applied to the UAVs they have to use. In Iraq they ended up with two Pioneer UAV squadrons. Each unit had eight UAVs. The Pioneer entered service in 1985. The 450 pound UAV requires small rockets to get it off the ground, and lands like any other aircraft. The UAV cruises at 120 kilometers an hour for 4-5 hours. The UAV can operate up to 180 kilometers from its control station. The U.S. Navy has been the main customer for the Pioneer, buying 120 of them for about $815,000 each. The U.S. Army had some, but turned them over to the Navy in 1995.