Set sometime in the 7th century, "Battlefield Heroes" depicts a humorous, yet intricate battle, between the Korean kingdoms of Silla, Goguryeo and the Chinese Tang dynasty. Rising Korean power Silla aligns with the Chinese Tang dynasty to attack its bigger Korean rival Goguryeo. Strategist Kim Yoo-Shin (Jeong Jin-Yeong) is intent on unifying Korea, but notices the Chinese desire to control the Korean peninsula. Kim then secretly conspires to join forces with Goguryeo to thwart the Tang dynasty's desire for expansion. "Battlefield Heroes" is a sequel to the 2003 film "Once Upon a Time in a Battlefield". "Battlefield Heroes" takes place 8 years after "Once Upon a Time in a Battlefield".