The Three Western Prefectures specifically refer to Xian Province, Luzhou, and Guanzhou.
Luzhou and Guanzhou border Qiyan. With numerous treacherous peaks and bizarre mountains within their borders, the two regions form a pincer formation. On the offensive, they can thrust directly into Qiyan territory; on the defensive, they can rely on the natural terrain to hold out indefinitely without falling. For many years, they have been a thorn in Qiyan's side.
Compared to Yue Province relative to Xiongchu, the temptation of Luzhou and Guanzhou to Qiyan is far greater.
Chapter 402