Mazer Rackham is the fabled hero of the previous Human-Formic war and Ender’s eventual teacher at Command School. Mazer is cold, quiet, and committed to his duty in much the same way as Colonel Graff. Unlike Graff, however, Mazer doesn’t show the potential for much affection, specifically toward Ender. Mazer believes his age excludes him from the ingenuity and spontaneous thinking needed to end the war for good. This is why he places his undying faith in Ender, deceiving the child commander in the process.
Mazer’s heroic reputation as the lone commander who won Earth its previous victory against the Formics awards him great levels of respect and power within both the International Fleet and the Earth as a whole. This reputation is why Ender resolves to take his relentless and cruel instruction without pushback. Mazer Rackham’s reputation also plays a large part in Ender’s eventual success, as Ender reveres his strategic ability so completely that he is able to replicate Mazer’s prodigal war performance. In the moment of his success, however, Ender does not realize he truly defeated the Formics as Mazer deceives Ender into believing the battle is simply another simulation. This deception further illustrates both Mazer’s strategic abilities and his dedication to the war.