What is the theme in Chronicles of the Crusades by Jean de Joinville?

In the second book, Joinville makes a clear statement throughout the novel about the power of God and how this power helps the Crusaders throughout their journey. In the beginning, the king is rescued from death by God, and thus goes on his Crusade. Throughout the journey, the king and Joinville both become ill several times, and thank God for their survival. Joinville even thanks God for his suffering, as he believes it is done to show him he has dome something wrong in God's eyes.