I didn’t say anything about genetic engineering, they can be regular humans.

Moreover, wars and conquest are not rational endeavors that are undertaken after a careful cost/benefit analysis. WWII wasn’t exactly cost effective for anyone who started that war.

Anyway, the way I see it playing out would be that Earth, realizing they are Mars’ one and only lifeline, will do its best to squeeze Martians for everything they’ve got. It won’t be a mutually beneficial trading relationship between peer nation/planets, but an exploitive one where one party has much more power than the other. Probably a lot like Africa’s place in the world. Unfair and exploitive deals will be cut that reflect the power imbalance, which will brew resentment and envy, and ultimately conflict. This is how you start irrational wars.