Audio problem: Sitting on the boat listening to the B-52 strike, when Clean says, "Charlie don't never see 'em or hear 'em, man." his lips do not match his words. (00:24:20)
Other mistake: When Chief Phillips tries to kill Captain Willard there's a shot of the captain's back in the bright sunlight. If you look closely at the center of his back below his right shoulder there's a pressure mark similar to what you see on a hot summer day after a person gets up from sitting in a beach chair for a while. On the PBR we see Martin Sheen's character standing for a long time throughout the entire scene, but he was definitely sitting for a while before this particular shot was filmed. The pressure mark is not in the previous shot. (02:23:20)
Continuity mistake: When they first approach Dennis Hopper we see the water on the left side of the boat past where Lance is sitting and there are no flames on it. After Hopper jumps on the boat and goes to shake the captain's hand we see an oil slick burning in the middle of the water. (02:29:40)
Continuity mistake: After Dennis Hopper walks around to the other side of the bamboo cage Captain Willard turns around to look at him. Now both his upper and lower lips are parched but when we saw him in a close-up before when Dennis Hopper said, "he likes you, he really likes you" only the captain's lower lip was parched. (02:43:50)
Continuity mistake: After the music for "The Ride of the Valkyries" is turned on there are several shots of the helicopters flying in formation and no speakers or surf boards can be seen on them. (00:38:10)
Continuity mistake: Chef says to Captain Willard, "I'm short and we gotta go up there so you can kill one of our own guys?" as Lance pulls Chief Phillips' body off the PBR and into the water. In the next shot he's already several feet away from the boat. (02:24:25)
Continuity mistake: As Chief Phillips yells, "you savages, come and get it" Captain Willard grabs him with his right hand to try and make him stop shooting. In the next shot he's holding him with both hands. (02:22:20)
Visible crew/equipment: Captain Willard says he made a deal with the playmates for all the guys and Chief Phillips says," you got some mama's in there?". You can see all the stage lights reflecting off their raincoats. (01:27:10)
Continuity mistake: While he's standing Col. Kilgore says, "I can take that point and hold it is long as I like". Chief Phillips' left hand goes from leaning on his leg to rubbing his face between shots at the beach party. (00:33:40)
Continuity mistake: Captain Willard thinks to himself about how many men he may have killed in the war and we see the PBR up close for the first time. The crew on this boat is not the same as the crew we'll be meeting shortly because at least four of them are white. (00:19:25)
Continuity mistake: In General Corman's residence Captain Willard walks past the dinner table and there's an extra light green plate between his plate and the chair that's not there later when he sits down for dinner. None of them went near the table. (00:10:20 - 00:11:40)
Continuity mistake: As Chef and Clean have a verbal fight after they leave the Medevac Lance is in the front of the boat putting on camouflage while holding a mirror in his right hand. In the next shot he's leaning on his right arm and holding the mirror in his left hand. (01:33:20)
Continuity mistake: The first time we see the severed heads there's a lot of white dry ice-like smoke to the right of Dennis Hopper. The next time we see this spot several seconds later the smoke is just starting to appear. (02:33:20)
Continuity mistake: When we first see the Frenchmen appear on the dock in the plantation scene there are eleven of them. The next time we see them as Captain Willard approaches there are four and a few seconds later another five more appear out of hiding. (01:57:55)
Revealing mistake: As Captain Willard takes his second swing at Colonel Kurtz there is a "spark" superimposed against the wall behind his head, which is to depict the contact point of the blade to the wall. However, the blade is actually resting on the Colonel's back, nearly a foot away at that time. (03:07:45)
Continuity mistake: As the Captain passes Francis Ford Coppola there's a flame throwing tank burning down a hut behind him. In the next shot after the helicopter takes off the flamethrower is gone and some Vietnamese wagons are there instead. (00:26:10)
Continuity mistake: In a close-up Chief Phillips he says, "sampan off the port bow" and we see a kaki green T-shirt hanging next to him at the right of the screen. A couple of shots later Captain Willard says, "what up chief" and Phillips takes the T-shirt down. In the next wide shot of the boat the T-shirt is back. (01:34:15)
Continuity mistake: At Kurtz's compound Lance sits at the front of the PBR watching them chop down the dead body hanging from the tree. The machine gun behind him rotates 45 degrees counter clockwise between shots. (02:34:30)
Continuity mistake: As the helicopters first attack there's a long shot of the Vin Din Dop beach and we can see the Viet Cong huts and none of them has a flag waving in front of them. In the next shot of the same spot we see two bright red communist flags. (00:39:50)
Deliberate mistake: None of the helicopter's in the movie have the Army markings seen on Vietnam era Hueys. The most you'll see is some crooked, faint and inaccurate stencils in the wrong spots. (00:37:50 - 00:51:25)
Chosen answer: Kurtz was protected by political connections and his military record from being relieved of command, and the Montagnard people whose village he was in were considered American allies, so they couldn't just send a force in to kill him or relieve him of command, but an individual assassin. (The US Government's "official" policy is that they do not engage in assassination, which is why "this mission does not exist, nor will it ever exist").
Captain Defenestrator