Sergius Saranoff, the Bulgarian cavalry officer in Bernard Shaw's Arms and the Man, is Shaw's vehicle for satirising the romantic idea of the heroic soldier. On the surface he is the dashing war hero; on examination he is brave but foolish, theatrical rather than professional.
The accidental hero. Sergius wins fame by leading a reckless cavalry charge against the Serbs at Slivnitza. It succeeds, but only by luck: the enemy had been supplied with the wrong ammunition and could not fire. Bluntschli, the professional soldier, dismisses the charge as the suicidal folly of an amateur, comparing Sergius to Don Quixote tilting at windmills. Militarily the charge should have been a massacre; Sergius is celebrated for an act of ignorance, not skill.
Romantic idealist, poor strategist. Sergius approaches war as a stage on which to display glory and honour. He knows nothing of the practical craft of soldiering that Bluntschli embodies, the man who carries chocolates instead of cartridges because food keeps a soldier alive. Precisely because he broke the rules of war and won, Sergius is passed over for promotion, a bitterness that helps to disillusion him.
Disillusionment. By the play's development Sergius grows cynical about the whole profession. He resigns his commission and delivers his famous verdict that soldiering is "the coward's art of attacking mercilessly when you are strong, and keeping out of harm's way when you are weak." The romantic hero comes to despise the very heroism the world praises in him.
The poseur off the battlefield. His conduct in love mirrors his conduct in war. He preaches the "higher love" to Raina while flirting with the servant Louka, proving that his heroic and noble poses are a performance rather than a settled character.
Conclusion. My impression is that Sergius is physically courageous but professionally incompetent, a brave but vain amateur whose reputation rests on accident and posturing. Through him Shaw deflates the glamorous myth of the soldier and champions instead the unromantic competence of the realist Bluntschli.