Superior resources, generally. In the particular case of the war ongoing when I was brought here, the invading planet's residents have a - not invalid - problem with the New United Nations Spacy, or the NUNS. Who are the military arm of the human government as it exists now, so while I work for an independent military force of considerable size on its own, we could also call on the NUNS to multiply our numbers several-fold.

[She doesn't sound terrifically fond of calling on the NUNS, though. Half because the Windermereans honestly had some valid reasons to hate them, and half because calling on them in that case had resulted in the deaths of the entire force that was sent.]