Hey, I thought of something. I haven't read the books, but from wikipedia,
"The effect of the war on the
psyche of the Conquest fleet soldiers is steep. Although they rapidly conquer and hold about half of Earth, they regard it as a dismal failure because the whole of Earth did not fall in days, and because there is still a war being fought at all. The Race view the war much as
Americans in the real-world
timeline later viewed the
Vietnam War: although the Race usually have the upper hand, they are taking staggering (to them) losses due to
attrition. Further, the Race have an extremely
hierarchical society where authority is never questioned. However, the Race's mounting losses and inability to conquer Earth gradually lead to splits within the ranks of the Fleet officers; disgruntled frontline soldiers in
Siberia mutiny against their officers (an unthinkable act in their culture), much as
French army units mutinied during
World War I, demanding new army leadership that would stop the high attrition they were suffering."
It would be interesting to see how you extrapolate that to huge changes in the Race's culture 70 years on.