First Blood

Seven years after his discharge, Vietnam War veteran John Rambo (Sylvester Stallone) travels by foot to visit one of his old comrades, only to learn upon his arrival that his friend had died from cancer due to Agent Orange exposure during the war.
Distraught, Rambo continues to travel, wandering into the small town of Hope, Washington.[5] He is intercepted by the town's arrogant and abusive Sheriff Will Teasle (Brian Dennehy), who considers him an unwanted nuisance. When Rambo asks for directions to a diner, Teasle drives him out of town and tells him not to return. Rambo does so anyway, so Teasle arrests him on charges of vagrancy, resisting arrest, and possessing a concealed knife.
Led by sadistic chief deputy Art Galt (Jack Starrett), Teasle's officers bully and abuse Rambo, triggering flashbacks of the torture he endured as a POW in Vietnam. When they try to dry-shave him with a straight razor, Rambo snaps, overwhelms the police force as he fights his way outside, and flees into the woods. A furious Teasle organizes a search partyâcomplete with automatic weapons, dogs, and a helicopterâto recapture him. During the search, it is learned that Rambo is a former Green Beret who received the Medal of Honor for his service. Galt spots Rambo and resorts to lethal force in defiance of orders, attempting to murder Rambo from the helicopter. He hangs from the outside of the chopper in an attempt to get a better aim at shooting Rambo. Rambo then throws a rock at the helicopter's windshield, fracturing it; the pilot is surprised and his sudden reaction causes Galt to lose his balance and fall out of the chopper to his death.
Rambo attempts to persuade Teasle and his men it was an accident and that he wants no more trouble, but the police open fire and pursue him into a wooded area. Rambo disables the deputies non-lethally one by one using his combat prowess, until only Teasle is left. Holding a knife to his throat, Rambo threatens to fight back much harder if he doesn't "let it go".
Teasle chooses to press the issue, and the Washington State Patrol and the Washington Army National Guard are called in to assist in the manhunt. At the same time, Rambo's mentor and former commanding officer, Colonel Sam Trautman (Richard Crenna) arrives in Hope. Warning of his former soldier's abilities, Trautman advises that Rambo be given a gap to slip through so he can be recaptured more safely later. Confident that Rambo is hopelessly outnumbered, Teasle refuses.
A National Guard detachment corners Rambo at the entrance of an abandoned mine; against orders, they use a M72 LAW rocket, collapsing the entrance and apparently killing Rambo. However, he survives, finds an alternate way out of the mine, and hijacks a supply truck, which he uses to return to town. To distract his pursuers, he starts a fire at a gas station, blowing it up, shoots out most of the town's power, and destroys a gun store near the police station with a stolen M60 machine gun to distract and locate Teasle.
Teasle, meanwhile, has positioned himself on the roof of his station to search for Rambo, and is spotted there by him in the confusion he created. The two engage in a brief gunfight, which ends with Teasle falling through a skylight, badly injured by Rambo shooting him through the ceiling. Rambo prepares to kill him, but Trautman arrives and warns Rambo that he will be shot if he doesn't surrender. Rambo collapses to the floor in tears where he talks about the things that happened to him in Vietnam and when he returned home. He then suffers a Post-Traumatic Stress Disorder-triggered breakdown before surrendering to Trautman, and he then is put into state custody and driven away as Teasle is sent to the hospital.

Question: Who Rambo's mentor and former commanding officer?
Answer: Rambo's mentor and former commanding officer is Colonel Sam Trautman.