In 1972, Cường, a
Hanoi Conservatory student, gives up the opportunity to study at the
Tchaikovsky Conservatory against his mother's wishes to enlist in the PAVN, and is sent to the PAVN-occupied
Quảng Trị Citadel. Quang, an officer of the opposing
Republic of Vietnam Military Forces, is tasked with retaking the citadel. While en route to the battleground, he encounters Hồng, a civilian, and protects her from harm. To reach the citadel, Cường and other recruits are ferried across the
Thạch Hãn River by civilian supporters, including Hồng. The two become enamored. Arriving at the citadel, Cường forms Squad 1 with Tạ, who assumes the squad's leadership; Bình, a former art student and artist; Tú, a high school student who requested to enlist via a letter written in his own blood while being underage; Sen, a brusque special forces soldier; and Hải, a steadfast former utility engineer. As they begin to defend the citadel from
Army of the Republic of Vietnam (ARVN) attacks, Sen becomes
increasingly shaken, while Hải discovers a sewer that can be used for emergency getaway. Meanwhile, the
Paris peace talks are underway, with negotiations being directly influenced by the battle in Quảng Trị. To gain grounds, ARVN orders its soldier to infiltrate the citadel and install their flags. While PAVN soldiers manage to thwart the attempt, Cường is injured after a direct encounter with Quang, and Tú is killed. Cường is nursed back to health by Hồng as their feelings for each other deepen. He refuses to be transferred back to the North for recovery, choosing to stay and continue fighting. Haunted by his defeat, Quang also returns to the battlefield. Squad 1 is joined by Tấn, a former college freshman, while Sen goes insane from psychological trauma. During another attack, while moving a delirious Sen out of harm's way, Tạ is fatally shot. Affected by his experiences, Cường begins to compose music. ARVN soldiers discover the sewer and use it to lure out and capture Hải. After failing to torture him into persuading his comrades to surrender, they burn him alive. Sen, who has snuck up to the scene, ambushes them with grenades and is killed in the ensuing chaos. Despondent at his comrades' fates, Bình loses composure during another battle, exposing himself to the enemy's line of fire, and is killed. An agreement on ending the war is reached, resulting in a ceasefire. As PAVN soldiers leave the citadel, Cường and Hồng reunite and affirm their devotions to each other. Cường volunteers to turn back to counter an impending attack by ARVN soldiers, entrusting his belongings to Hồng. At the end of the battle, he engages in melee combat with Thái, another ARVN officer, and then Quang. Cường ultimately triumphs and decides to spare Quang's life. Thái, who has been holding grudges against the latter, opens fire at both. ARVN soldiers who witness the act kill him, as Cường and Quang succumb to their wounds. Tấn, having been sent away from the battle by Cường, is Squad 1's sole survivor. Years later, during peacetime, Hồng, Cường's mother, and Tấn are seen in the audience as Cường's composition, titled
Red Rain, is being performed by an orchestra. ==Cast==