Cairdre is a heavyset, rather stupid-looking squirrel, less quick and agile than others of his kind, but he does his job just fine. Even though he was thrown out of the army, he still insists on wearing his armour and regulation tunic as a mark of pride, since he's convinced himself that he's the only creature in the lower city with proper military training.
As mentioned before, Cairdre has a kind of military pride about him. He walks about with his back straight and his chest puffed out, but inside, he's really quite unsure of himself. He's relatively young to be an officer, and being relieved of his duties and cast down to live among the very creatures he was paid to control is an incredible blow to his ego. Even worse is the discovery that quite a few of the aforementioned creatures are just as brave and tough-some in fact braver and tougher- than he is. Being very aware of this, he tries to use his military standing to gain respect. Unfortunately, the effect is countered somewhat by the obvious fact that he's absolutely terrified of Raitha.
Cairdre was a minor officer in Lightail's army, until he was framed by some of his comrades, arrested, and relieved of his duties. The rest is explained in the history of the inner city rebellion.