In 2003, while digging up remains at a Korean War battlefield to set up a memorial site, a South Korean army excavation team notifies an elderly man that they identified some remains as his own even though he is still alive.
Five decades earlier, in June 1950, the Lee family goes about their lives in the South Korean capital of Seoul. Lee Jin-tae owns a shoeshine stand to pay for his younger brother Jin-seok’s education. Jin-tae has also bought them a silver pen, a precious item the brothers share, and is working on a pair of immaculate shoes for his brother to wear to school. Jin-tae’s fiancée, Young-shin, works with the Lees’ noodle shop. On June 25, 1950, North Korea invades South Korea, and both brothers are forcibly conscripted. They are assigned to the 1st Infantry Division, fighting at the Pusan Perimeter before advancing north upon the successful U.S. amphibious landing at Inchon. Jin-tae is told by a superior that if he can earn the highest award for a South Korean soldier, the Taeguk Cordon of the Order of Military Merit, his brother can be sent home. Jin-tae volunteers for many dangerous missions and performs suicidal acts of bravery to earn the medal, and is quickly promoted to sergeant. His heroism during the urban Battle of Pyongyang finally results in Jin-tae’s nomination for the medal, but his combat experiences have made him into an emotionless killer, which horrifies his younger brother.
The U.N. coalition is eventually forced to retreat all the way back to Seoul when the Chinese enter the war on the North Korean side. Jin-tae finally earns his medal, but in Seoul, Young-shin, suspected of joining the Communist party during the Communist occupation, is arrested by a South Korean militia, and the brothers attempt to stop them. During the struggle, Young-shin is shot dead, and the brothers are arrested for trying to rescue her. In jail Jin-tae’s request to release his brother is refused, and the security commander orders the prison set afire with the prisoners inside when the enemy forces approach. Trying to rescue his brother, Jin-tae loses consciousness and wakes up believing Jin-seok died in the fire. He murders the surrendering prison warden before being captured by Chinese soldiers.
In truth, however, Jin-seok had been transferred to a military hospital after barely escaping, rescued by “Uncle Yang”, a now-disabled veteran from their old unit. Jin-seok learns that his brother had defected to the North Koreans and now leads an elite North Korean formation known as the “Flag Unit”.
Jin-seok chooses to rejoin the Army, which has by now retaken all of South Korea with U.N. support. He demands to be allowed to fight, at the 38th parallel, but is denied. Jin-seok eventually defects, claiming to his captors he is Jin-tae’s brother. The North Koreans, however, believe Jin-seok is a spy and are about to take him away for interrogation when their position is attacked by U.S. and South Korean forces. The attack frees Jin-seok, who continues his search as the position is captured in a vicious hand-to-hand battle. Before the U.N. forces can secure their gains, however, the “Flag Unit” arrives, tearing into them with Jin-tae at its head.
The brothers come face-to-face, but, not recognizing Jin-seok, Jin-tae attempts to kill him, and Jin-seok barely avoids death before his brother is briefly incapacitated. Jin-seok attempts to carry him away but is shot in the leg. With both of them wounded, Jin-tae finally recognizes his brother, and the two have a tearful reunion. This is cut short, however, as the North Koreans force back the U.S. and South Korean troops. Jin-Tae orders his brother to save himself. Jin-seok initially refuses but relents after Jin-Tae promises that they will meet again. As the wounded Jin-seok limps to safety, Jin-tae mans a machine gun and provides cover fire for his brother and the other South Koreans before being killed.
In 2003, the elderly Jin-seok stands at the excavation site; the remains initially identified as his are those of Jin-tae. He examines Jin-tae’s few excavated belongings, including their long-lost silver pen, and begs his brother’s skeletal remains to speak to him, quoting his promises as his granddaughter looks on with sympathy.
Back in the 1950s, in the aftermath of the Korean War, Jin-seok returns to his mother, who also survived, discovers the shoes to which his brother had dedicated himself to perfecting, and heads off with Young-shin’s younger siblings in a now-peaceful, but ruined, Seoul as the nation begins rebuilding. He reassures them that he will return to school, fulfilling the promise he made to Jin-tae.