Easy. It's an infinite loop. You will win and need more missiles. You lose glory and need more missiles. The game is made to force the player that you need diamonds for glory and missiles. Do you want to be the best? I would rather enjoy my character than worry over the math behind it. Don't get so worked up about it. Smile:) It will make you feel better.
To make films, sometimes part of the mission is duels and up to 25 or more of them to complete the film, I do enjoy the game, that's why I've been a daily player since I started, but like everyone, I've always got questions, you don't know if you don't ask and I only use earned diamonds within the game, my bought ones are used for my studio.