What is the theme in Shadow of the Giant by Orson Scott Card?

The theme of ambition is introduced in the first chapter when Han Tzu is offered the opportunity to leave earth to colonize one of the former Hive Words. Instead, he chooses to stay in China and in the same day is offered control of China's military, but it is not enough. "Turning around to face the open door, Han Tzu said, 'There is no one in this building with the authority to command me" (P. 20). The themes in this book are interrelated and the member's of Ender's Jeesh, including Han Tzu, were originally chosen because they tested as highly ambitious. Not necessary for self but to be the best.