This doesn't really take into account a nation's ability to buy up military before a large conflict. For example, I just dismissed a third of my max troops and most of my tanks last week to save on bills. It wouldn't take anything to rebuy them, but that's not reflected in your rankings. Only what's on hand is counted. This favors larger nations as they can afford to keep a greater military presence on hand, thus giving alliances with a greater number of large nations a higher ranking. Don't get me wrong, I like the idea, I just think it is another way of looking at alliances with the highest average nation score.