The so-called Princess Yongle in the poem title was actually Yang, the granddaughter of the King of Dongping during the reign of Emperor Xuanzong. She married Li Shihuo, the King of Khitan. Yang was granted the title of Princess according to convention because of her meritorious service in marrying foreign nations. Sun Ti was an official of the Tang Dynasty, so the poem used exaggerated descriptions to describe the beauty of Princess Yongle and showed the desolate appearance of Lulong Pass at that time.
诗题所谓的永乐公主其实是玄宗朝东平王的外孙女杨氏，嫁给了契丹王李失活，杨氏因为和亲番邦有功，依惯例被封为了公主。孙逖为唐朝官员，因此诗里用夸张的形容描绘了永乐公主的美丽，并且表现了当时卢龙塞荒凉的面貌。
《观永乐公主入蕃》 孙逖
边地莺花少，年年未觉新。
美人天上落，龙塞始应春。
Princess Yongle on the Frontier
Sun Ti
Orioles and flowers are few on frontier;
Nor new birds nor new flowers come with new year.
The fair princess seeems to fall from the Sky;
Spring comes to Dragon Fortress far and nigh.
