Arms and the Man is a comedy in the broadest sense of the word, meaning it is not a tragedy: nobody dies and nothing terrible happens. It's also a comedy in the narrower sense that its situation is played for laughs: it is a light-hearted caper about mishaps in love and war.
It's anti-romantic, however, in that it is an attack on stereotyped notions of romantic love and war heroism. (Romance, in general, paints an idealized picture of the world.) Bluntschli, the play's real hero, is a deserter who carries chocolate bullets rather than real bullets that could kill. He tells the truth about the war rather than a fairy story, saying for example:
Soldiering, my dear madam, is the coward's art of attacking mercilessly when you are strong, and keeping out of harm's way when you are weak. That is the whole secret of successful fighting.
He exposes Sergius, Raina's fiancé, supposedly a dashing and brave army officer, as a man who won his recent battle only because the other side was more grossly incompetent than he was. The play also reveals Sergius as only pretending to be in love with the upper-class Raina, while carrying on with her maid. The play, though lighthearted, punctures romanticized ideals of love and war.