Raina doesn't know exactly what she wants. She has been raised to marry a man like Sergius and to hope for him to be a hero. She has also been raised to be sweet and kind and never to lie. It's difficult for her to admit that these things are impossible for her. When she meets Bluntschli, it is her first experience with the idea that gray areas exist. Not all soldiers are brave, not all cowards are bad, and not all lies are unforgivable.
Bluntschli is a very practical sort of fellow. He wants to make money by being in the war, but he doesn't particularly want to die. However, he isn't as cowardly as he would have Raina believe, and he also isn't as mercenary. He doesn't want to hurt anyone. Rather, he wants adventure and to live his life.
Sergius is a very conflicted character. He has always believed that he has to be a certain way—a brave soldier and a worshipful admirer to Raina. The war and the servant Louka challenge these beliefs. He comes across as sort of a cardboard cutout of a man, but he wants to be more than that.
Catherine is presented as a very typical woman of her era. She can be bribed by her husband with pretty things, as with the bet over a piece of jewelry. She sets a standard for Raina to be a perfect woman who never lies or does anything wrong. In fact, she does lie to her husband, as she is never really herself around him. She is also very concerned about what people think. She worries people will think the Petkoffs are low-class for yelling for the servants or because Raina made a poor marriage.
Petkoff is smarter than his family would believe. He sees what is going on most of the time. He realizes Sergius is something of a buffoon and also that Raina put a photograph in the coat for someone to find. He also realizes the coat was missing in the first place. He is not an expert on military tactics, but he knows he isn't and is willing to delegate.
Louka is very clever, and she sees everything. She is the one who tells Raina that the shutters can be opened, and she knows that someone can come in. Although she isn't Sergius's equal in class, she is more than his equal in intelligence. She feels she shouldn't be kept down by her low station. Moreover, she is not willing to degrade herself.
Nicola is a man who knows his place and wants to be safe. He doesn't want to defy the Petkoffs, and he warns Louka against doing so. However, in the end, he is willing to give up his claim on her to see her rise in class. He is a capable servant and hopes to be rewarded for that in the end.