Most Redguard [I]are[/I] very talented fighters, since they are a fairly martial society and they're raised from birth to be warriors. 

From the Wiki, 

[I]Redguard society is extremely martial, and nearly everyone is expected to have a grasp of basic weaponry and combat, although only the rulers are generally expected to have any knowledge of strategy, formations and tactics. Only the strongest, fastest and smartest Redguards are accepted into the demanding military (which consists mainly of various knightly orders), and they are expected to prove themselves worthy by facing death. Even their entertainment, like snake charming, bears some risk to it. The practice of eastern magic is greatly frowned upon by Crown and Forebear alike, and outsiders are not tolerated in many parts of Hammerfell.

They are a highly disciplined and enterprising people, having centuries of experience with warfare in their homeland. Their warriors are acknowledged to be among the best in the world. The Redguards are also known for their naval prowess, and their fleets have proved a match for the Empire's best armadas, as seen during the Stros M'Kai revolt. Stros M'Kai and some parts of mainland Hammerfell hold many Dwemer ruins, and some young Redguards seeking to enter military service must brave the dangers of these ruins. Most of their holidays and traditions seem to revolve around either the celebration of natural phenomena or the commemoration of great battles and warriors.[/I]

As for Captain Ismal, it would be best not to underestimate him. You need to ask yourself what kind of man commands the loyalty of a highly effective and ruthless group of guards, especially in this kind of society.