What is the theme in Lioness Rampant by Tamora Pierce?

Duty drives most of the characters of this story. Despite her arguments with Jonathan, Alanna still recognizes him as her king, even before his coronation. She feels that it is her duty as sworn knight to do what ever will best serve his reign as king. It is out of her sense of duty that Alanna braves civil war in a hostile nation, roving bandit groups, and brutal snows as well as the powerful elemental who brought them about, all to bring the Dominion Jewel back to Jonathan. When she returns home, her duty will call her to fight to put down a rebellion at the hands of a powerful sorcerer.