During my deployment I've run into several different categories of animals that we interact with. I hadn't realized it, but there are 2 types of working dogs in the military.
There are the K-9 units. These dogs work with the military police and are trained in specific tasks such as sniffing out narcotics, explosives, or trained to assist in enforcement. I think most people associate this kind of job when they think of a military working dog.
The second type of official working dog are therapy dogs like Butch. Butch is one of several dogs in theater that are assigned to the mental health teams. She happens to be here with us at our combat support hospital. Her job is to help put the patients at ease. She is a very well-trained and affectionate dog. You'll notice she has a "uniform" that she wears. All working dogs have a rank. It is typically 1 rank higher than the individual that works with them. By doing this, if the handler ever caused any harm to the animal, it would be considered assaulting a senior NCO. On either side of her uniform is her unit, and for fun they have also placed patches for many of the units also stationed here at COB Speicher that she works with.
Now there are also some "semi-official" animals here in Iraq. I don't have a picture of "Rosie", but she is a mascot that was brought over with one of the units that runs our base. She is officially sanctioned by leadership, but she hasn't been through the training that Butch has, and her role is more to boost the morale of the Soldiers from her unit. She's not as friendly, and I've had her actually bark at me - so I don't care for her too much.
There are also the "non sanctioned" animals like this one. These ones are usually strays that are adopted. It is illegal to have them, but people tend to ignore that at times. I've even heard of them being released from traps by individuals who don't want to see them taken away by vector control.