As of the expositional passage of the first scene, Raina and her mother are swept up in a nationalist frenzy of battle-glory and valor. This befits their sheltered, upper-class social milieu. Sergius, the returning hero of the battle that had raged beyond the perimeter of town, has cloaked himself in soldierly romance. The portrayal of heroism or bravery one step removed from the front lines is, to some degree, still actually brave and heroic. But it seems as though all of Sergius’s energy goes into appearances and self-aggrandization.
Bluntschli, by contrast, has no status or options; forced into service and pinned in, he has to live on instinct and wit. That he begins in such a negative state, and rises—essentially—to become a peer among the family fighting men, is in itself a testament to his resourcefulness and core integrity.
There’s reason to believe, based on Shaw’s treatment of other characters in his plays—like arms merchants directly responsible for destruction-for-profit, or someone like the play-acting Sergius—that the author favors the Dove (the man of peace) that fights when he must, rather than the Hawk that puts on the best display.