They are most likely being supported by what is known as a "Forward Support Battalion".
This unit provides all aspects of support to the front lines.. such as fuel, food, maintainance, and a few combat medics in with the mix..
I've been in both kind of support units... the "Forward Support Battalion" and the "Main Support Battalion"
The Forward Support basically tags behind the front line providing immediate support. They are far enough back behind the front lines, in void of immediate enemy fire.. but close enough to the front lines, to give support at a moments notice..
The Main Support Battalion is most likely located on a main camp in the main combat zone. They provide support to the Forward Support Battalion. They also provide maintainance support for the things that the Forward does not do. Forward Support basically does a "break, swap & fix" routine... Main support would then take that part, and do the detailed technical mainainance of whatever was broke. Being out on the Forward side of things, you are worried about getting the tank, missile system, or whatever it is you are working on fixed in the shortest amount of time possible..