The humans are the French. Their homeland is conquered early on in the war, leaving only resistance fighters who use guerrilla warfare and sabotage tactics to harass the invaders. Though unable to provide large-scale military help, their intel on enemy movements prove to be invaluable to the war effort and the tide of the war is turned when their homeland is re-invaded by the Allied forces. They even have the same reputation, if Garrus' joke is any indication:
Garrus: All right, my turn. What's the first order an Alliance commander gives at the start of combat?
Joker: Uh...I give up.