The Chaucer Review: An Indexed Bibliography (Vols. 1-30)

Hatton, Thomas J. "Chaucer's Crusading Knight, a Slanted Ideal." 3 (1968): 77-87.
The Knight's portrait emphasizes two virtues--worthiness and wisdom as defined in the 1380s and 1390s. As a worthy man, the Knight has bravery, skill, and battle experience. He is also wise in choosing his actions to conform to chivalric ideals. Though the Knight will fight for his lord, the specific battles in which the Knight has fought demonstrate both his worthiness and his wisdom: in his primary battle experience has not fought other Christians, but has been a crusader, fighting the heathens. These characteristics suggest that the Knight represents a chivalric ideal proposed by Philip de Mézières and his Order of the Passion of Jesus Christ.

Pratt, John H. "Was Chaucer's Knight Really a Mercenary?" 22 (1987): 8-27.
The campaigns in which the Knight participated are legally crusades in that the Church or Christians are threatened. The Knight seems to have received more than religious satisfaction from his knightly activities, but such remuneration is not unusual for this period when all military men received compensation for their service. The military encounters follow the pattern of those of a knight whose lord commands him to fight in an unjust war. Though the Knight may have served in Turkey, his behavior still falls within the law. None of the Knight's campaigns are against other Christians. Thus the Knight is not a mercenary.