Plot hole: When Rambo hijacks the Army truck, he throws out the driver, Robert A. and continues driving down the one-lane dirt road in the same direction. When Robert A. hits the ground, he immediately pops up and runs the opposite direction, away from where the truck is driving. A couple of shots later, we see a behind view of Robert A. running. It turns out that it is the driver's view from a Sheriff's vehicle. How could a car, especially a Sheriff's squad car, possibly come from that direction since it was a one-way road? And how could that same officer not see that the man driving the truck was Rambo?
Plot hole: The national guard leader says a dozer wouldn't be able to get to that area where the mine was blown up which supposedly was around 500 yards from where Trautman and Teasle were dropped off in the helicopter. But in the following scenes Rambo crawls through the mine which is nowhere near 500 yards long and when he comes out of the shaft he's right next to the road filled with trucks and other vehicles. So why can't a dozer get there?
Chosen answer: Because it's a knife that someone else is holding and can use against him. It's common for people in dangerous professions to regard their weapons as tools. For example, police officers who commit suicide by handgun rarely use their service weapon, but rather a personal firearm.
Captain Defenestrator
Additionally, I believe it is made clear during that scene that Rambo had previously been tortured at some point, and one of the tools used was a knife. So the combination of being restrained and having someone approach with a knife caused him to basically have extreme PTSD and so he attempts to escape.
oldbaldyone