Ning Yuan, a modern martial arts grandmaster, travels through time to the northern frontier of the Great Yu Dynasty and becomes a low-ranking frontier soldier at Yanmen Pass. Just as the imperial court distributes convict women to military households, he unexpectedly receives three women with tragic pasts: Yun Chuqing, Mu Lan, and Baili Qinghan. Facing the lustful advances of the greedy and brutal squad leader Ding Sanpao and the threat of invading Tatars, Ning Yuan uses modern military tactics and formidable martial arts to fight on the battlefield and repeatedly earn outstanding merits. Framed by powerful figures within the army, he is banished to defend the dilapidated and dangerous Tieshi Fort. There, he gathers refugees from Qingzhou and fights off a much larger Tatar army. Amid internal strife and external threats on the turbulent frontier, he rises step by step from a lowly soldier, protects those around him, and carves out a remarkable legacy.