I'm trying to understand how to parse the がってんなら in this sentence (it's from Tales of Vesperia, in case anyone's curious):
帝国がってんなら、 この旅の間にも 何度か見てきたろ？
This is how it's translated in the English version of the game:
Haven't you already seen what the empire's capable of several times on this trip already?
The second part of the sentence is easy enough, but I just can't wrap my head around the first part. Is it short for 帝国があっているなら or something? And what would that translate to literally? Is there some bit that's omitted that I should be able to infer from context?
Thank you :)