At this point in the war, the French just want to get out of Russia as fast as they can. They resent having to provide for Russian captives and have no incentive to treat them well. Knowing what he does about the behavior of soldiers under duress, Pierre is fearful, and yet he’s able to find humor in the situation—showing the new joy and simplicity he’s uncovered while imprisoned. The sky reminds him of eternity and the fact that a soul, like the sky, can’t be held captive.