In the year 1375, a small political envoy embarks on a journey to China to meet the esteemed Ming Emperor. However, a grave misunderstanding leads to their arrest, as they are mistakenly identified as spies. Amidst this turmoil, their transport is ambushed by Mongol marauders, resulting in the brutal killing of the Chinese guards and allowing the Korean envoys to escape. As fate would have it, all the Korean ambassadors are lost, leaving the inexperienced general to take charge of the situation.
The soldiers quickly arm themselves, discovering that the Mongols have kidnapped the Ming Emperor's daughter. In a bold move, they launch an ambush to rescue the princess. Among the brave warriors is Yeo-sol, the former slave of an ambassador, who engages in a fierce duel with the injured Mongolian general Rambulwha. Ultimately, Yeo-sol triumphs but, showing mercy, allows Rambulwha to escape.
With the princess in tow, the Koreans are determined to return her to the Ming Emperor, seeking to atone for their diplomatic blunder. However, the Mongolian forces are in hot pursuit, eager to reclaim the princess and marry her to the Yuan Emperor, thus solidifying his claim over China. The Koreans aim for a seaside fortress, mentioned by the princess, which they hope will serve as a sanctuary. Along their arduous journey, they are joined by a group of Chinese peasants, all fleeing from the clutches of the Mongols.
As they navigate through the clashes with Mongol search parties, the Korean group faces numerous internal struggles fueled by social class tensions, love interests, and notions of honor. The lower-class soldiers feel the sting of their poor treatment compared to the upper-class soldiers and harbor little faith in their young general, often preferring the leadership of the veteran sergeant, Dae-Jung. Meanwhile, the princess grapples with her new reality, struggling to adapt to the rigors of their desperate situation.
Tension escalates between the general and Yeo-sol as they both vie for the princess's attention, leading to several confrontations. Upon reaching the fortress, they are disheartened to find it nothing more than a dilapidated ruin. As the group braces for a final stand against the Mongol forces, the princess attempts to sacrifice herself for the sake of her rescuers. In a dramatic twist, both the general and Yeo-sol leap into action to save her, leading to Yeo-sol's subsequent capture.
In an unexpected turn, Rambulwha extends an offer to Yeo-sol to join his ranks, but as the Mongols prepare for a vigorous assault, Yeo-sol chooses to return to his fellow Koreans. In the ensuing battle, the Koreans face disaster when their gunpowder defenses malfunction. In a heroic act, Yeo-sol gives his life to save the princess. The final showdown concludes with the general meeting his end at the hands of the Mongolian general, who also loses his life in the clash. All Mongols fall in battle, while the remaining Koreans are decimated, leaving only Dae-Jung alive.
The princess decides to stay with the peasants at the fortress, pledging to relay the courageous sacrifice of the Koreans to her father. With a heavy heart, Dae-Jung constructs a boat and sets sail back to Korea, carrying the weight of their lost comrades.
