When all land is equally worthless, conquest needs no justification but conquest itself.

[There was power in a flag, in the nation it represented. The pitiful water tribes were hardly worth the ice they floated on, after all, but the Fire Nation would rule them nonetheless. It was destiny manifest. A cause which gave Azula's words a tone of utter conviction- one granted to her from a lifetime of being raised under nothing but such an ideology.]

And the matter of the gems, I suppose.