Chapter 1: Sir, Chapter 2: The border is in a state of emergency. What novel is it?

The opening of Datang played a psychic role. Chen, the author, wrote in the first chapter of this psychic travel novel with the opening of the Tang Dynasty as the protagonist that Mr. Title introduced the origin of the protagonist Li Yi 'an, and in the second chapter, the title Li Yi 'an just crossed the border and was in an emergency, so he wanted to recruit him as a soldier.