I've taken out 5 empire armies and secured a fort on middenheim and suddenly the empire pulls up with 4 more

okay maybe they just snowballed or something and had money

but then i see a empire faction i turned into a vassal had 3 full armies 8 turns after i made them?
middenland or something like that

now i lost my main horde completely, lost my chaos fort in middenheim and im at square one only because i got enough pop for a spare horde in norsca but due to my main horde being down ill lose that soon because my vassals sure as hell aint gonna tolerate me