Why did Xiao Xixia survive for so long during the confrontation between Dali and Liao in the Northern Song Dynasty?

Xixia is indeed a small country with few people, but because of its remote geographical location, it is not a battleground for military strategists, and the dispute between Song and Liao benefited him to some extent.

The national defense construction of the whole people absorbed the political and legal system of the Song Dynasty, and the indomitable national spirit even made the Song Dynasty feel a powerful threat for a period of time.