The answer to this question can be found at the end of Chapter 5, which charts the end of the first battle Henry has participated in and his feelings about it. What characterises this battle above anything else is the way in which it has been a ramshackle, chaotic affair, with soldiers not really knowing what they are doing or where they are going. In particular, what defines the battle is the complete role of chance in determining whether a soldier lives or dies. Military skill, strength or valour seems to have no weighting in giving you a greater chance of surviving, as the injuries and deaths of various soldiers narrated in this chapter demonstrates. Yet what strikes Henry above all else at the end of the chapter is the following thought:
As he gazed around him the youth felt a flash of astonishment at the blue, pure sky and the sun gleamings on the trees and fields. It was surprising that Nature had gone tranquilly on with her golden process in the midst of so much devilment.
Nature is presented as being an impersonal force that carries on with her job regardless of what is going on beneath her and around her. The sky remains "pure" and "blue," signifying the "tranquil" way in which nature has been carrying on with her work in spite of the bloody happenings of the battlefield. Nature is indifferent, and the battle that has been such a massive focus for Henry is nothing to it, and this is a realisation that surprises Henry