The term later on evolved to describe the dynamics that exists between a warrior and his Lord. Comitatus holds that while both are still in the battlefield, actively fighting, neither lord nor warrior can leave the scene of battle for any reason. Both entered the battle, and both should leave at the same time. This may be where the “leave no man behind” phrase comes from. This agreement that exists between Germanic Lords and his subordinates is believed to have given rise to the feudal system, where the serfs owed to their feudal lord.
Some scholars maintain that there is no break between the original comitatus of the Roman Empire and the vassals of the Middle Ages (Powicke, 1949, 92) Chivalry describes the virtues practiced by the knights of the Middle Ages. It is hard to place a specific definition to chivalry, but it is a moral and social code which advocated honor, courage, and respect. When we talk of chivalry, we conjure images of a knight in shining armor, ready and able to rescue us from our dire circumstances (Frantzen, 204, 1)
Comitatus is a code that binds soldiers to their commanders, while chivalry is a code that binds men to the principles of honor and virtue, wherever they may be. While both concepts refer to relationships and values, comitatus is more about loyalty and courage in battle, while chivalry is more about loyalty and courage in all aspects of life. Chivalry presupposes comitatus, but comitatus does not necessarily mean chivalry.