James Cameron's original screenplay began with Colonel Trautman finding Rambo in a psychiatric hospital instead of a prison. The psychiatric hospital concept was instead depicted in Terminator 2: Judgment Day (1991).
Co-writer James Cameron claims that he only wrote the first draft of the script and that Sylvester Stallone made many changes to it. When the film was released, the political content of the movie was considered controversial. Many felt the Vietnam War was altered to look and sound heroic. Cameron commented that he only wrote the action and that Stallone wrote the politics.
Rambo's stats, as given in the film: "Rambo, John J., born 7/6/47 Bowie, Arizona of Indian-German descent. Joined army 8/6/64. Accepted, Special Forces specialization, light weapons, cross-trained as medic. Helicopter and language qualified, 59 confirmed kills, two Silver Stars, four Bronze, four Purple Hearts, Distinguished Service Cross, Medal of Honor."
According to the documentary We Get to Win This Time (2002), the producers considered teaming up Sylvester Stallone with his Staying Alive (1983) protégé John Travolta (who was once considered to play Rambo himself in the first film) as Rambo's young partner in rescuing the American POWs. Stallone nixed this idea when he decided it would be better to make the film a solo project.
The original title was First Blood II, but Sylvester Stallone decided he wanted the series to be named after the lead character, just like the Rocky series. So he re-titled it "Rambo: First Blood Part II" so he could name the third film Rambo III (1988) instead of First Blood III.
The only movie in the Rambo franchise in which Rambo shares an intimate kiss with a woman (the female agent Co). In First Blood (1982) there were flashback scenes of Rambo at a Saigon bar kissing and making love to a Vietnamese prostitute, but those scenes never made it into the final cut.
All of the shots of the military base were done on a Mexican Air Force airstrip. The logos have been painted over or obscured, and the real crew always have their backs toward the camera or are far enough away from the camera so no one would notice.
In First Blood (1982), Colonel Trautman's Green Beret flash is that of the Army's 5th Special Forces Group. In this movie, and the sequel (Rambo III (1988)), he is shown wearing the flash of the 1st Special Operations Command, which means he was reassigned after the events of First Blood.
According to the stats given by Murdock, Rambo has 59 confirmed kills during the Vietnam War. However, Rambo kills 74 people during the course of the film, which spans two days. So, in two days, Rambo kills more people than the whole of the war.
Sylvester Stallone said of the first draft: "I think that James Cameron is a brilliant talent, but I thought the politics were important, such as a right-wing stance coming from Trautman and his nemesis, Murdock, contrasted by Rambo's obvious neutrality, which I believe is explained in Rambo's final speech. I realize his speech at the end may have caused millions of viewers to burst veins in their eyeballs by rolling them excessively, but the sentiment stated was conveyed to me by many veterans.... [Also] in his original draft it took nearly 30-40 pages to have any action initiated and Rambo was partnered with a tech-y sidekick. So it was more than just politics that were put into the script. There was also a simpler story line. If James Cameron says anything more than that, then he realizes he's now doing the backstroke badly in a pool of lies".
George P. Cosmatos had Murdock and his men snacking in one of the scenes to show their apathy toward the mission. Oliver Stone showed George W. Bush eating food during meetings in W. (2008) for similar reasons.
At the end when Rambo is flying the chopper and happens to pull beside the Russian Helicopter, one of the POW's is firing a mini-gun. It shoots a 7.62 round at 3600 rounds a minute. It would have ripped that copter to shreds. The rate of fire is so much, that 2,3,4 bullets hit the same spot with one pull of the trigger, even if you swing it around. The 7.62 round would easily go through the armour and when it killed the guy inside, 500 more bullets going inside would have destroyed all the electronics. When he shoots them from the front, it would have shattered the windshield and punched its way through killing both pilots. That's why it's real name is Bullet Resistant Glass. Enough shots from a .22 would eventually go through let alone a 7.62 firing at such a high rate would penetrate quickly.
The trivia items below may give away important plot points.
As Co Bao (Julia Nickson) died in Rambo's arms after the ambush, there was supposed to be a triple zoom-in while Sylvester Stallone screams "No!" echoed 3 times. During a test screening, audience actually started laughing. It was quickly re-edited to the present form.
At the end of the novel "First Blood" by David Morrell, John Rambo dies, which doesn't allow for sequels and ends on a dark note. The ending was changed in the movie, allowing for this sequel to be made.
In a rare alternate take of the ending scene (when Rambo says, "I want, what they want, and every other guy who came over here and spilled his guts and gave everything he had, wants! For our country to love us as much as we love it! That's what I want!"), Rambo wept as he told this to Trautman. A behind-the-scenes video of this take can be seen in an episode of Entertainment Tonight (1981) from the mid-to-late 80s.