This dissertation explores the way that war formed the Northern Song (960-1127) state. Earlier research on the Northern Song failed to explain how and why the Northern Song empire established a peaceful border with the Liao empire to its north. This dissertation, by means of a detailed military history of the period from 954-1005, concludes that the Liao state did not intend to destroy the Song state. It was the Liao's limited military and political goals rather than the strength or weakness of the Song that created a peaceful border between the two empires.