How did Shaw use wit and humor throughout the play?

Shaw uses irony to create humor in this play that shows the absurdity of war and exposes false heroism. Captain Bluntschli, the seemingly dishonorable deserter from battle, proves to be more sensible and honorable in the end than the dashing Colonel Sergius Saranoff.
Raina and Sergius have a highly conventionalized romance. She thinks she loves him because he is a heroic military man who won a battle. In fact, as Bluntschli shows, Saranoff is a blunderer who won the battle only because the leadership of the other side was more grossly incompetent than he was. Sergius also pretends to be nobly in love with Raina, but he is actually carrying on a romance with her maid, Louka. Shaw uses a double entendre in the "arms" of the play's title: not only do Sergius's "arms," in the sense of weapons, show him to be a false hero, his "arms," as in "arms" as a body part embracing a loved one, are also false. 
Shaw's humor can unfold easily because he has created a comic world. Nothing really bad happens in this slightly zany, almost enchanted space. A soldier breaks into Raina's bedroom, but she has nothing to fear. They only talk. Sergius betrays Raina for Louka, but that does not matter either: Raina's "love" for Sergius was only skin-deep anyway. In this safe space, the comedic can unfold unfettered.