From the point when Micheal takes over the family until the day he settles all family business, Michael is very secretive. For very understandable reasons. Afterall, the future of the family depends on the success of his plans, and he had prepared for every eventual outcome. He even created new secret regimes. He could not take any risks.

The Corleones were in a weak position. Micheal (& Pop) had plans and kept them to himselves. The caporegimes were getting pressure from the other families, and were worrying that they'd come under Barzini's thumb sooner or later.
They doubted the fact that Micheal was not to the job of leading them to better times. Micheal asks them to 'hang in there'.

I started to think that Tessio would probably not have turned if he didn't feel that the situation was hopeless and that their leader had lost their mind. He was after all asking them to give in to the enemy, not recruit any men, and to basically allow the empires they were responsible for to crumble. Ask them to blindly entrust their lives and livelyhoods to a plan the the new kid boss thought up and without any reassurances. Logically, shouldn't Michael have at least have thought about the prospect of loosing Vitos best caporegime, or any other valuable employee.

In all fairness, he did say that there were things being negotiated that would answer all their questions. I felt that if he had put the message across more clearly, he may have prevented a traitor. I'm not saying that he should have disclosed any details of what was gonna happen or even hinted at it, but he could have made it more obvious by saying "You dont know whats going on. I do, and I give you my word it will work out. Trust me or else...".

But he was very vague, and didn't reassure them. He made them leave the meeting openingly doubting him (this comes across clearer in the book), almost as if to tempt one of his valuable employees into turning. He knew his employees were businessmen, that they were smart, and that Tessio was always smarter. Why tempt them?

I couldn't really see why until I formed a theory yesterday. I propose it is for the sake of suspense in the narrative. At this point, even the audience feels that the family is in trouble, they are weak, the other families are moving in. We're meant to feel it is hopeless. The tension builds until the it reaches a massive climax. And, as an extra bonues, the audience gets an additional execution and an additional traitor, which adds to the climax.

So, what I am proposing is that maybe Micheals failure to reassure his employees that things would be OK was not a logical move for a Don to make - he lost Tessio. Maybe it was a vehicle to build suspense isntead. Micheal being careless maybe?

I think it was more a case of Michael acting like his father but not having the confidence of his subordinates. If Vito had said, "Dont worry, everything is being worked out, I cant tell you how, but I give you my word it will be ok," then perhaps Tessio would have stayed on board.

But with Michael taking over, and with the Don old and sick, and with the fresh memory of what a bad Don Sonny was, Michael's reassurance did not convince Tessio that the Corleones could get themselves out of the mess they were in unscathed.

As Mike later said, "It was the smart move. Tessio was always smarter."

Certainly it was a move to build suspense and bring us to the big climax--The Great Massacre of 1955. After all, if things had gone along swimmingly for the Corleones, we wouldn't have had the great ending and the trial by fire/anointing of Michael as the new Don Corleone.

But I also believe there was considerable logic in Michael's seeming failure to give his caporegimes the iron-clad reassurance they might have wanted to stay loyal. He was testing them. At that point, their loyalty to Vito was unquestioned and had endured decades of friendship. But Michael was new, relatively unknown and unproven in their eyes. His primary objective was to eliminate the other Dons and make himself omnipotent in preparation for moving to Nevada. But his secondary objective was to assure himself that he'd face no disloyalty within his family that would interfere or derail his primary objective.

Don't forget that Vito backed Mike in these plans. Vito went as far as to ask for his capos patience, trust and understanding. Tessio wasn't prepared to give that to Mike.

There's iron logic in everything he does. He is not only testing them. He appears weak on purpose. I wrote a really long article about this meeting once... In short: Carlo is a traitor already, and possibly may spy for Barzini. One of caporegimes, as they suppose with Vito, may go to Barzini and betray as well. Whoever it is, he will inform Barzini about everything said and unsaid on this meeting. That's why it's so important for Michael to assure all three of them that he has absolutely no ace in his sleeve. The betraying capo is a chessman sacrificed in combination. Whoever it is, Michael decides much more important task than keeping him loyal to the Family.

Right. When they didn't like what they heard from Mike they went to Vito, and I think it was Clemenza who said that he wanted to go off with Tessio and form their own family. Thats when Vito sort of endorsed Michael by saying if you trust my advice then be a friend to Michael. At that moment Tessio and Clemenza knew the Don's days were over, and they had to decide whether or not Michael had it in him to continue running a successful family.

I have pointed this out before, and I think it is telling...notice at the end of the scene TESSIO shaked Mikes hand with his LEFT HAND, which I always thought was a giveaway as to who the traitor would be.

To say nothing of the fact that he (Tessio) brushed right past Vito after that. (Clemenza shook hands with Vito AND Clemenza was the only one to respond to Vito when Vito asked if he had their trust).

Yes, indeed. When Vito asked, "Do you trust my judgment?" Clemenza responded, fervently, "Always, Godfather." Tessio hissed: "Yesss." Another giveaway.

Turnbull

I don't remember Tessio saying anything at all. I thought it was only Clemenza responding to Vito? I haven't seen the movie in a few months and could be wrong.

This issue is also addressed in the novel. I wish I could remember how Vito phrased it in the novel because it was better than I'm describing it. Something to the effect of always having your enemies underestimate you.

Michael was building a new family. That's why Neri and Lampone were recruited and promoted. Out of respect for his father and to minimize any opportunity for outright rebellion, he retained Clemenza and Tession. But, those two were his father's guys. He needed capos who would be loyal just to him. So, he was willing to risk some treachery. In fact, he probably expected it.

I suppose this was another example of Michael playing the percentages. Eliminating every risk that could spoil his plan.

Goombah, I don't have the movie here with me, but I'm sure that, if you listen closely in that scene, you'll hear Tessio hiss, "Yesss..." FFC probably made that remark subdued to emphasize Tessio's diffidence.
I also don't have the novel with me. If I recall correctly, Vito did not make the remark about underestimate/overestimate to anyone in particular--I think (and I could be wrong) that it was one of those passages in which Puzo states Vito's philosophy. After the caporegimes leave, Tom, Vito and Michael are together, and Tom asks, "Why am I out?" That's when Michael tells him that he's not a wartime consigliere. He leaves the office, telling Michael that he thinks Tessio is right about moving against Barzini. Then Vito tells Michael that the hardest thing is to have to hurt those closest to you--as in telling Tom that he's out.

Wow, I never picked that nearly inaudible response by Tessio. I'll check it out Turnbull. Thanks for the insight!

Exactly, not to mention he needed to bring in some "new blood" so to speak into the familyu business (BTW didn't Kay get a hint that Mike was not going to go legit when he brought in people to replace Tession and Clemenza?).

Here it is, Turnbull:
And the second one, only for you.

Tom finished his drink and before he left he gave Michael a mild reproof. "You’re nearly as good as your father," he told Michael. "But there’s one thing you still have to learn."
"What’s that?" Michael said politely.
"How to say no," Hagen answered.
Michael nodded gravely. "You’re right," he said. "I’ll remember that."
When Hagen had left, Michael said jokingly to his father, "So you’ve taught me everything else. Tell me how to say no to people in a way they’ll like."
The Don moved to sit behind the big desk. "You cannot say ‘no’ to the people you love, not often. That’s the secret. And then when you do, it has to sound like a ‘yes.’ Or you have to make them say ‘no.’ You have to take time and trouble. But I’m old?fashioned, you’re the new modern generation, don’t listen to me."
Michael laughed. "Right. You agree about Tom being out, though, don’t you?"
The Don nodded. "He can’t be involved in this."
Michael said quietly, "I think it’s time for me to tell you that what I’m going to do is not purely out of vengeance for Apollonia and Sonny. It’s the right thing to do. Tessio and Tom are right about the Barzinis."
Don Corleone nodded. "Revenge is a dish that tastes best when it is cold," he said.

Many thanks, JustMe.

Prego, prego. Just remember that I’ve done you a service.

I cannot agree that he is "retaining" them out of respect and changing them because they are his father's people. I would say the situation is far easier: Michael is moving to Nevada. The NY operations must be left to someone friendly, so Clemenza and Tessio are to form their own families. Being capos of their own families, they cannot be Michael's capos and follow him to Nevada.