“You see, sleep or no sleep, hunger or no hunger, tired or not tired, you can always do a thing when you know it must be done. Well, that pipe must be got down...”
Bluntschli speaks this in Act One, in conversation with Raina when hiding in her room. The quote indicates his thought processes as a person and as a soldier. After all, Bluntschli is a mercenary. He fights as a Swiss with the Serbians because they have paid him to do so, because it is his occupation. This means that the war does not seem to touch the deepest part of him. He’s not invested in it as an outcome of good against evil. But he is invested in it as a man doing his job, and for whom that kind of work is important. Thus, when Raina says that he must leave her room, he knows what a soldier must do is obey a woman in her social position.
He seems to recognize that as a soldier, his life is dominated by a desire for food and a desire for sleep. And in this instance, he has satisfied at least part of that, by eating the chocolate creams that Raina has given him. But he is not yet willing to abandon his desire for sleep, because he has gone so long without it, and because his very ability to reason seems to be slipping away. Yet, again, he is willing to toss all this to the side in order to do what an obedient man of honor would do, which is to leave the room of a woman who is asking him to do so.
All these opposing forces are at play in Bluntschli’s decision-making. He has a desire to preserve his life, and also a desire to do what Raina asks. He has an obedience to principle as a “good” soldier, and also an obedience to whatever puts those principles into action, which is the overwhelming fear any solider has of injury or death. Bluntschli demonstrates a kind of rational self-mastery that will only be overturned by Raina’s willingness to let him nap for part of the evening in her room.