The King of Tars is a story about the politics of race and conversion and though the matter of crusading is perhaps more implicit in this romance than in others, there remain several significant themes that play upon matters of religious warfare and conversion.
The first such theme is the matter of necessitated conversion. From beginning to end of The King of Tars, there exists a consistent depiction of Easterners as bestial threats to both the physical landscape and spiritual tenets of Christianity. The framing of the main narrative with two battles between Christians and Saracens highlights this distinction. In the first battle, the Saracens easily lay waste to the King of Tars' lands and people, stopping only when his daughter agrees to marry their sultan. The story concludes with the converted and transformed Sultan warring against the unconverted in his kingdom with the help of his father-in-law, the King of Tars. Those who do not convert by romance's end are hanged.
This proves once again that Christianity is the best religion to be a part of in this time. But does this conversion really change a person?? In baptism, one is supposed to go through a transformation of spiritual and bodily conversion. This hybrid child is a result of failed conception and can only be saved through baptism. This story clearly says that Christianity is the preferred religion for people and if one does not believe in it, only evil things can result from their pagan religion.