Rambo's knives, over the course of the series, reflect the development of the character through the years. At first, they're finely honed and crafted with a touch of finesse - especially the one in the third movie - much like Rambo himself; in the first three movies, he's physically well-defined, and rather than just plowing through the enemy, uses skill and cunning - his "hide and seek" tactics in the second and third movies come to mind. Come the fourth movie, his knife, while certainly a deadly instrument, has none of the artistry of the previous blades; it's best described as a simple mix of a machete and meat cleaver. Rambo himself, at this point, just seems to be an instrument of war and death - muscular yet bulky, and rather than the usual cat and mouse tactics, he simply devastates the enemy soldiers with a .50 caliber machine gun. In the fifth movie, peaceful Rambo who has settled down comes armed with a knife that looks very similar to his first one; switching to a homemade cleaver after losing it to the Cartel, once again symbolising how far he has regressed.
Seeing Major Pa Tee Tint with the Jericho 941, even if it's not the standard sidearm, should give you an idea on who's been arming the Tatmadaw over the years after the West began to cut Myanmar from buying arms due to human rights violations.
Murdock in the second film looks a lot like Sheriff Teasle from the first film. No wonder Rambo didn’t trust Murdock, aside from the fake sob story and him betraying Rambo.
In the fifth film, why did Rambo lose so badly to the cartel in his first encounter with them? Age and a red mist certainly played their part, but we also have to remember that his skill set lies in Vietnam AKA jungle warfare. Urban warfare simply is not something that he has the same level of experience in. The only reason he got away with non-jungle warfare in Afghanistan was a) he is still a relatively young man and b) between Colonel Trautman and the Mujahideen, he actually has more help in this film than he does in any other. Its also worth noting that there was a lot of tunnel fighting in Vietnam, which again, plays back to why he does so well in both Three and Five when he finally led his enemy underground.
