When the shuttle Tyderium is attempting to sneak onto Endor Vader notices that Luke is on the craft. His mission is to acquire Luke for the Emperor, and that is what happens later, so why does he allow the ship to land? Why not just capture it right there and then? Bring Luke to Sidious? What exactly is prompting him to let them pass? It's not a scheme of Vader's since immediately afterwards he goes to tell the Emperor about it.
It's a mindgame. There wasn't really an exact timeline for Vader to bring Luke to Palpatine. Whereas the Rebel assault was going to happen immediately. They knew that whoever is on Shuttle Tyderium are part of a bigger mission for the Rebels. So rather than alert the Rebels that the Empire knows what is happening, they allow them to proceed, resulting in the Rebels playing further into Vader and Palpatine's trap.
I've never quite followed Vader's moves in ROTJ. Last he speaks to Luke in ESB, he's trying to recruit him so they can together overthrow the Emperor. Had Luke said yes to that, I don't think Vader's first move would have been to bring him before the Emperor. Now in ROTJ, for all Vader knows, he could still turn Luke to his side. Why tell the Emperor that Luke is nearby? All it did was make the Emperor slightly suspicious of Vader's intentions. Was Vader no longer interested in having Luke join him against the Emperor?
Vader let the shuttle go because he was more concerned that Rebel saboteurs were aboard than his son, who wouldn't have come in a shuttle if he was there for him. He would have come in his X-Wing as he did at Cloud City. Vader felt it was imperative to report the shuttle first and then tell Sidious about Luke. PALPATINE: "I told you to remain on the command ship." VADER: "A small Rebel force has penetrated the shield and landed on Endor." PALPATINE: "Yes, I know." VADER: "My son is with them."
I wouldn't say it's so much of a mind game, cause Luke even knows Vader can sense him, it's probably specifically the Emporer's directions down to the last bit. This will allow them to put the Rebels on the moon and destroy them with the secretly operation DS, if they think they're safe and about to succeed there will be no chance of them escaping. Vader couldn't exactly pull over the shuttle, grab Luke and send the rest of the Rebels on their way to the generator. And, he wants Luke to join him willingly, he wants Luke to come to him instead of intimidating him and forcefully imprisoning him.
Well, not quite. Palpatine says that Luke will come to Vader and when he hears it, Vader is surprised. PALPATINE: "In time he will seek you out." VADER: "He will come to me?" PALPATINE: "Yes, and then you will bring him before me."
Vader is professional and cunning. But like the others said, he's conflicted. You can tell there is a lot going on inside his head during his first in-person conversation with Luke on Endor. He feels pride for how powerful Luke has become, he doubts that he made the right choice by not remaining a Jedi, he is somewhat jealous of Luke, he's afraid of Sidious, he's wondering if he should let Luke kill him to take his place, and he's wondering if he can still overthrow Sidious with Luke's help. The guy is a psychological mess until he makes up his mind and chooses the right thing in the end.
The Emperor's plans included the Rebels landing on Endor, so Vader was always going to allow the shuttle to pass. But I take it that he didn't expect Luke to be on the shuttle,hence his hesitation. Rather than risk mucking up The Emperor's plan by holding the shuttle,he did the smart thing and let things go as planned and brought the situation before the Emperor.
I think the reason that Vader is hesitant is for the reason you said: Making sure the Rebels landed was part of the plan. Luke was nervous because he could feel Vader's conflict. He knew he would be screwed either way. He suspected Vader and Sidious were setting a trap for them by letting them land, but his initial thought was along the lines of, "How are Han, Leia, Chewie, the droids, and these soldiers going to be safe if Vader tries to force the ship into the Executor?" If he and Vader had a fight, he would be concerned for the safety of all involved. As much tension as they had in the throne room during their duel, at least they had had time to think about what was going on. If they went into a duel right in the docking bay of the Executor, Vader would be an immediate threat to everyone in that tiny ship except Luke. It might take him thirty minutes to kill Luke, but it would take him one minute to kill the other Rebels and ten minutes to kill Leia.
Well it wasn't like Vader was going to say 'open fire commander' was it? I think Vader felt something but didn't know exactly whether it was definately Luke, similar to him feeling Obi-Wan's presence in ANH. May be he felt a trace of Leia's presence too, after she seems to tap into her Force potential killing Jabba other force users may sense her now.
Without getting too far off topic, that part of the plan never made much sense to me. Couldn't they have just jammed their transmissions and captured the shuttle anyway? The Rebel Fleet was coming one way or another - as we see later with the whole "shield is still up" scene. There was no point in letting them even land, quite frankly. I guess having Luke's friends be in peril while he was on the Death Star was some kind of motivator to turn him to the dark side. Seems like having Han and Leia locked up while the rebel fleet gets completely slaughtered would do the trick just as well.
Then there would be no Ewok battle. Not to mention that originally, Palpatine orders Jerjerrod to blow up Endor right before the duel begins. Which is what finally starts the duel.
Funnily enough, Vader says it with the same surprised inflection as when "Nixon" said "sock it to ME?":
It's predicated on the shield generator blowing up though: The Emperor hissed. "Your fleet is lost — and your friends on the Endor Moon will not survive..." He pushed a comlink button on the arm of his throne and spoke into it with relish. "Commander Jerjerrod, should the Rebels manage to blow up the shield generator, you will turn this battle station onto the Endor Moon and destroy it." "Yes, Your Highness," came the voice over the receiver, "but we have several battalions stationed on—" "You will destroy it!" The Emperor's whisper was more final than any scream. "Yes, Your Highness." - which doesn't happen until the end of the duel. Right after the shield is destroyed, the Emperor starts blasting Luke with Force Lightning, in the movie.
I think he does this simply to make sure no obstacles get in the way of Luke's capture. If they hold them in the shuttle they may escape before TIE fighters or a tractor beam can intercept them.
Vader let Luke go because he knew his son would come looking for him, to save him & he knew together they could defeat Palpatine.
W Well - sentimental family values somewhat? I mean Anakin - remember some say he was always - his heart was really in the end with the Light Side of the Force - he is the Chosen One afterall in a sense! AND he really just wanted the best for Padme and to stop Death but due to Palpatine never 'giving a Force' about his promises of Power and such ... sadly Anakin gets corrupted ... AND consider one way or another Anakin must have been forever scarred not just physically but also mentally - and the fact Padme's loss and the pain and anguish of it ... consider Luke and Leia are the only traces then left then of his flesh and blood and of Padme - as a part of Padme so hence he may have had second thoughts or turned a blind eye momentarily? I mean also considering how Anakin wanted Luke to join him ... AND how he reckoned he could 'get Leia to convert' as Leia too was Force-Sensitive...
