[Celjabba]

No-one deny that if you are the only one with a decent size TL11 army, you can crush any TL8 army.

BUT in order to have that army (and everything it implies), you need to build it first - which means money, labs, factories, training, workforce, time.

You cannot use your army-of-doom to grab the ressources you would need to build your army-of-doom.

So, either you handwave having seized a country back when it was easy (ie, before WW1 or thereabout) or in modern time you start small and out of the way and pray you can hide what you are doing long enough that when someone realize what you are, you have become too dangerous too obliterate/have evolved enough diplomatic ties to convince other nations to let you live.

Either way, we are as stated above in comic book territory regarding economy and politics.