While a respect for authority may well be part of the oath soldiers take, I have heard rumors, likely apocryphal, that at times soldiers hold their superiors in less than the highest regard. There are even rumors of soldiers bitching about those in higher command.
While there might be lots of support in an all volunteer army for a task such as the Iraq war, in this particular instance there are also a large number of troops in the field that were from the Reserves and National Guard who may well have been watching their family business go down the tubes because they were called up.
Aslan is not a Tame Lion