Emergence of warlords/partisan leaders
(Yes, for freedom, liberty, king & country, fascism - im sure, in somalia and afghanistan they have great causes too )
Soldiers of the leash.
War feeding the war.
Refugees pouring back and forth.
Source is mostly anecdata:
My late grandfather was a Nazi truck-driver in France, Italy, eastern Europe (Hungary, Greece) and the stories he and his war companions told - are really very similar to those you get to hear from African refugees.
My grandfather and his officer made a nice little extra by smuggling people and got sentenced into a "Straf-battalion" for taking advantage of the general lawlessness of the situation.
I know, i know- the popular Nazi image in TV presents a wicked law & order extremist, but where the war went - it really was quite different. There was a mixture of total lawlessness (as in "We dont care/expend resources on subhumans") and extreme military overreactions.
And before you claim that was just fascism at work, as if politics where just a program loaded into humans, no,the unraveling usually set on before the occupation got started.
In a ironic way, the Nazis and their homecoming war proofed that all humanity, disregarding of race, pushed beyond a certain breaking point - is equally wretched and desperate.
A zombie like animal, forgetting about tomorrow, trying to see the end of today at all costs. Not a beautiful sight, but one that offers a lot to understand and learn.
The good news is, once the stress is reduced - and the war has not gone on to long, preventing the education of the next generation- there is a way to recover.