“I have no ambition to shine as a tradesman; so I have taken the advice of that bagman of a captain that settled the exchange of prisoners with us at Peerot, and given it up.”
Sergius complains in Act Two about precisely the view of soldiering that Bluntschli holds. Bluntschli thinks that being a solider is simply fulfilling a job that entails loyalty and courage without necessarily being honorable. For Sergius, being a soldier has much more to do with issues of pride and self-regard. After all, Sergius led the doomed charge on the Serbians, which succeeded only by luck, because he wants to look the part of the soldier and commander. As many characters note, and as Sergius himself is willing to admit, he does not have the natural skill in warfare that Bluntschli does. He will never be promoted through the ranks as others might be who understand the art of war. Rather than admit to war as an art or craft he does not possess, Sergius instead resigns his commission.
This marks the beginning of Sergius’s slippage from a position of moral authority in the work. Soon thereafter, he begins flirting seriously with Louka, who is shocked by his duplicity as regards Sergius’s engagement to Raina. And when Sergius finally loses Raina to Bluntschli, he winds up marrying Louka, a woman who is looking to improve her own social station by finding a nobleman willing to “stoop” to marrying her.