Not man, but food supply.
Remember Ainz also have 3 kingdom to feed.
Overlord
Xavier Robinson
Joseph Richardson
>Not enough man power
Ainz can shit liches and death knights. A single lich with two death knights and a soul eater is enough to take over a city if you subjugate the local population and form your own militia.
Kevin James
You clearly don’t know how a country operate if you think liches and death knight are what kept a nation running. The amount of problems for running a country is massive.
And even if Ainz spend a whole decade making liches he would still not have enough to run a nation nor have the time to properly train them.