Veteran's Experiences Allegory
The narrative surrounding Stephen's experiences during World War One are allegories of the experiences of the real-life veterans that the author spoke to in doing his research for the novel. This is most likely why the imagery of the battles of the Sommy and Ypres are so graphic and brutal; they are directly taken from the memories of the men who were there, and from their own experiences.
Stephen's Coded Journals Symbol
When Elizabeth finds her grandfather's journals she also discovers that they are written in a code. Although this would have been something that all soldiers did at the time, in case their journals got into enemy hands, the fact that they are coded is also a symbol of the way in which history is also a code that needs to be deciphered in both the context of its own time, and in a contemporary context, so that it can be learned from and better understood as it informs the present.
Coded Journals Symbol
Stephen coded his journals. This is a symbol of the fear among Allied troops of their writings getting into enemy hands and being used as a source of information about strategy, the way things were done, or weaknesses that could be exploited.
Forbidden Love Motif
Both Stephen and his grand-daughter experience the emotional pain of forbidden love; Stephen is in love with Isabelle. When their relationship first begins, Isabelle is married to someone else and so their love is forbidden. When they flee together Isabelle discovers she is pregnant and panics, disappearing without telling him. By the time he tracks her down the war has broken out. When they meet during the war, Isabelle is in a relationship with a German soldier by the name of Max, and afterwards, her health has taken a turn for the worse; she dies from complications to influenza.
Elizabeth is also involved with a married man, and has a child with him. Throughout their relationship their love has been forbidden because of his marriage, but at the end of the novel it is implied that he has left his wife and that he is committing to a future with Elizabeth and their son.