In the following passage from Act 1, Bluntschli reveals to Raina that her betrothed behaved in a naive and silly manner on the battlefield; Sergius, it turns out, is not the brave hero Raina envisioned. In his description of Sergius's actions during the battle, Bluntschli alludes to Miguel de Cervantes's epic novel Don Quixote (published 1605/1615):
MAN: He did it like an operatic tenor—a regular handsome fellow, with flashing eyes and lovely moustache, shouting a war-cry and charging like Don Quixote at the windmills. We nearly burst with laughter at him; but when the sergeant ran up as white as a sheet, and told us they’d sent us the wrong cartridges, and that we couldn’t fire a shot for the next ten minutes, we laughed at the other side of our mouths.
The protagonist of Don Quixote is a man obsessed with the concept of chivalric romance. At the beginning of the novel, Don Quixote sets out on a mission to serve his nation by reinstating the chivalric principles of knighthood, lost to an earlier time. Cervantes's protagonist provides an important locus of comparison for Sergius, who remains invested in the Romantic masculinity and notions of chivalry belonging to a bygone era.
In the following set of stage directions from Act 2, Shaw describes Sergius using an allusion to "Childe Harold's Pilgrimage," a long narrative poem published between 1812 and 1818 by Lord Byron:
He has acquired the half tragic, half ironic air, the mysterious moodiness, the suggestion of a strange and terrible history that has left him nothing but undying remorse, by which Childe Harold fascinated the grandmothers of his English contemporaries. Altogether it is clear that here or nowhere is Raina’s ideal hero.
"Childe Harold's Pilgrimage" follows the adventures of a young, melancholic nobleman who travels across Europe. The poem is credited with establishing the Byronic hero as a common literary type (examples include Heathcliff from Brontë's Wuthering Heights). These romantic heroes are categorized by their brooding, mysterious nature. Often simultaneously intelligent and deeply troubled, Byronic heroes tend to hide their trauma behind a veil of charisma. The above passage clearly situates Sergius as another in a long line of Byronic heroes, representing the Romantic and "traditional" worldview for the purposes of Arms and the Man.
Sergius's status as a Byronic hero is cemented by an earlier passage in the same set of stage directions, in which Byronism is referenced directly:
[He] would not be out of place in a Parisian salon, shewing that the clever, imaginative barbarian has an acute critical faculty which has been thrown into intense activity by the arrival of western civilization in the Balkans. The result is precisely what the advent of nineteenth century thought first produced in England: to wit, Byronism.
The connection established between Sergius and Byron deliberately situates the former as an anachronism. Sergius's behavior and principles do not suit him to the modern technologies of warfare and their derivative horrors.