Mountains and Rivers Are Cold with a Knife

A modern polytechnic man traveled through time and became an orphan of the border army. In the chaotic world of low martial arts, with a sword, a sense of faith, and a little knowledge of objects, he went from an assassin in the Jianghu to a famous border general, and then from a chess player in the mountains and rivers back to the world. Finally, he understood: a knife can kill enemies, soldiers can defend the country, and only friendship can never be betrayed.