The film begins with Colonel Sam Trautman, portrayed by Richard Crenna, arriving in Thailand to once again recruit Vietnam veteran John J. Rambo, played by Sylvester Stallone, who has made a life for himself in the region since the events of First Blood Part 2. After observing Rambo's prowess in a stick fighting match, Trautman finds him at a Buddhist temple construction site and proposes a daring mission to Afghanistan. This operation aims to supply the Afghan rebels, known as the Mujahideen, with weapons, including FIM-92 Stinger missiles, to assist them in combating Soviet forces during the Soviet-Afghan War. Although Trautman shows Rambo distressing images of civilians suffering under Soviet aggression, Rambo declines to join, prompting Trautman to venture alone.
In Afghanistan, Trautman and his troops are ambushed by Soviet forces while navigating the treacherous mountain terrain at night. Captured, Trautman is imprisoned where Colonel Zaysen, played by Marc De Jonge, and his subordinate Kourov, portrayed by Randy Raney, attempt to squeeze information from him through coercive means. Meanwhile, Rambo learns of Trautman’s dire status from embassy field officer Robert Griggs, played by Kurtwood Smith, and persuades Griggs to facilitate an unofficial rescue mission, despite Griggs cautioning him that if he is killed or caught, the U.S. government will deny any involvement.
Rambo swiftly heads to Peshawar, Pakistan, where he encounters Mousa Ghanin, played by Sasson Gabai, a weapon supplier who reluctantly agrees to guide Rambo to Khost—a remote village near the Soviet base holding Trautman—after Rambo resorts to threats. The Mujahideen leaders, including their chief Masoud, portrayed by Spiros Focas, are initially reluctant to cooperate, especially after a Soviet helicopter attack is triggered by a leak from Mousa's shop. Demonstrating his formidable combat skills, Rambo thwarts the assault using a 12.7 mm heavy machine gun to shoot down a Soviet helicopter.
With only Mousa and a young boy named Hamid, acted by Doudi Shoua, by his side, Rambo launches a plan to liberate Trautman. His first attempt fails catastrophically, injuring both Hamid and Rambo, who must tend to his wounds after aiding Hamid to safety. The following day, Rambo re-attempts the rescue by stealthily scaling a cliff to bypass detection. He arrives just in time to save Trautman from looming torture. After liberating other prisoners and commandeering a Mil Mi-24 helicopter, their escape is compromised when the helicopter crashes, forcing the duo to flee on foot.
In a tense confrontation within a cave, Rambo and Trautman eliminate several Soviet special forces, including Kourov, but are soon surrounded by an overwhelming number of Soviet tanks led by Zaysen. As Zaysen demands their surrender, Trautman poses the question, “What do you say, John?” Rambo’s response, as he readies his weapon, is unequivocal: > "Fuck 'em." Just as they are encircled, the Mujahideen warriors, alongside Mousa and Hamid, launch a remarkable cavalry charge, turning the tide of battle against the Soviets. Amidst the chaos, Rambo manages to eliminate Zaysen by driving a tank directly into Zaysen’s helicopter.
As the dust settles from the fierce clash, heavily injured but triumphant, Rambo and Trautman bid farewell to their Mujahideen allies, concluding their journey through Afghanistan. The film wraps up with two poignant quotes: "This film is dedicated to the gallant people of Afghanistan," and "I am like a bullet, filled with lead and made to kill."
