What is the theme in Birdsong by Sebastian Faulks?

A significant portion of this novel, all of the parts set in England in 1978-1979 in fact, focuses on the importance of history as seen when Elizabeth attempts to learn about her grandfather, especially his involvement in the war. In "England 1978," Elizabeth becomes interested in learning about her grandfather's life and the war. In "Albert," she is struck by the magnitude of the war memorial. When she finds Stephen's journals in her mother's attic, she tries to decipher them since they are written in code.