Trivia: Brian Dennehy falsely claimed to have served and been wounded in the Vietnam War. He later apologized for the lie.
Trivia: When Rambo escapes the local jail, he slide-kicks and then elbows a sheriff's deputy in the face, leaving him lying on the floor screaming in pain. Sylvester Stallone accidentally broke the stuntman's nose in that take and the stuntman's screaming is real. The producers used the footage in the final film.
Trivia: Lee Marvin, Robert Mitchum, Gene Hackman and Charles Durning were considered to play the role of Sheriff Teasle.
Trivia: Al Pacino, Robert De Niro, Clint Eastwood and Michael Douglas were considered to play the main role of Rambo.
Trivia: In a deleted scene on the First Blood Dvd, Rambo is sitting by the fire when he begins to experience a flashback to a bar. The bar scene shows Rambo's encounter with a woman, with whom he was romantically involved. The background music playing in the bar, bears an uncanny resemblance to "Sunshine of your love" by Cream. The song has a few minor differences, but the progressive of the song is the same.
Answer: At the start of the film when Rambo is causing all these problems, the Sheriff has no idea who John Rambo is (Vietnam War hero), so he thinks Rambo is just another America-disrespecting drifter (the American flag on Rambo's jacket). Also, Teasle is a law and order guy who does not want his town disturbed by outsiders. After the fireworks and Teasle finds out who Rambo is and also meets Colonel Troutman, Teasle's mission becomes personal: rage at the death of his best friend, humiliation in front of his deputies, the incompetence of the state National Guard to subdue Rambo, and also a generational factor: Teasle probably served in Korea or WW2, when America was top dog in the world, so he will not allow some hippie ex-soldier from a "lost" war best him.
Scott215
That's it. When they got the news that Rambo not only was a real war veteran, an ex-Green Beret, he was a war hero with a Medal of Honor; if Teasle's ego was Pearl Harbor, getting that info was December 7, 1941.