We know Mike was an uber-controller, but he's not immortal.
Why didn't Mike want an underboss, at least as a precaution in case something were to happen to him? Don Vito had plenty of close people with him that could have operated the family if he met an early demise (Sonny, Clemenza, Tessio), but Michael didn't have anyone.

GF3 gave us Vincent. BUT, at this point Michael was old, and wouldn't an underboss need to be groomed for a number of years to successfully transition power?

Do you all here think Michael ever considered who would take over after him?

He intended to groom Anthony as his successor. We see that in the bedroom scene after the Tahoe shooting, and at Michael's party in the beginning of III. When the chips were down, he trusted Tom to run the family while he was away, temporarily.

BUT: No, he did not have a succession plan in place in case of death ("natural or otherwise") before then. As you said, Vito could rely on Sonny to run the family, and Sonny did after Vito was incapacitated. But, if Michael had been killed in the shooting, or didn't make it back from Havana, there would have been a (probably) bloody struggle for succession.

Isn't it the whole idea that Michael is trying to turn the family legitimate? I mean by III it's still very much the Corleone crime family, but he's left all that to Pentangeli in II and Zasa in III. So I don't know if Michael feels the need to structure whatever he controls like his father did. It's all a bit confusing to me, but that's the point, he says he's going legit, but everything tells us the opposite.

BTW, wasn't Fredo Corleone listed as the Underboss on that FBI chart or something like that? It's obviously a figurehead position though.

Yes, his goal was to be legitimate, but he was nowhere near totally legitimate in II (as when he danced with Kay), and the Tahoe attack showed just how vulnerable the family was without a succession plan. Even in III, he had no succession plan until he finally anointed Vincent near the end.

He probably didn't trust anybody to do the job or more accurately there was no living relative who could do the job.

If the succession war got bloody, my money would be on Neri.

Did Neri have the brains or just the power though? Mind you I think Neri was a capo so his intelligence must've been held in higher regard than his "predecessor" Luca Brasi.

Not only was he a capo, but he was Mike's right hand man in GFIII before Vincent came on the scene. I'd say Mike thought he had the smarts.

Neri was mostly a very efficient killer who knew how to get a job done. That's what's made him important for Mike, besides his "undying loyalty".

I think Neri was for Mike as what Carmine Galante was for Joe Bonanno. Some think Neri was also a psychopath, but I'm not sure about that myself.

Neri was eventually sent ot take over Tessio's regime which was probably temporary. But his primary role from day one was as Mike's majordomo, Mike's Luca. The novel makes it clear that Neri was pretty much a psycho, but he knew how to get things done. Vito didn't have an underboss either.

I always thought that once he was old enough Santino was considered the de facto Underboss? Despite Clemenza's and Tessio's seniority it was pretty clear who was in charge after Vito got shot.

Natural selection in that situation, but there was never any mention of Sonny as underboss.

At the end of the flashback chapter which covers Vito's early days up until World War II it's stated that Vito was considering making Sonny his underboss. It's presumable that this happened.

Would Neri have made any worse a Don than Sonny?

Or am I under-estimating Sonny?

Sonny was able to organize soldiers on the basis of loyalty. Vito must have introduced him to many of his political friends.
Neri, on the other hand, is a bulldog. Even during the conversation with Geary it's clear that Neri's only function is to check him out where to bite.
In the novel Neri is mentioned after the Moe Greene meeting:

Sonny is present at the meeting where Tom briefs him and the Don about his trip to California. He is also present (for the most part) with Hagen and the Don at the wedding where the guests are asking for favours. Clemenza and Tessio are present at neither of those things. So, although blood certainly played a part wouldn't his presence indicate that he was a part of the family's administration?

Sonny was part of the family's administration. He was made a caporegime in the mid 1930s and possibly underboss around 1940.

There was some disagreement over this earlier in the thread.

Apparently neither Puzo nor FFC saw any need to introduce an underboss. In fact, FFC also eschewed a consigliere in II probably for the same reason. Those two positions just did not serve any purpose in the films' narrative. As a further example, it apparently did not serve Puzo's purpose to assign the Corleones more than two capos longterm.

I love the role of 'consigliere', was always fascinated by it. I would have liked to have seen more about it...

I had always chalked up the no Consigliere in II to the fact that it gave Michael an illusion that his end of the family was legitimate or going legitimate.

How could that be? It comes straight out of the novel.

This is the post showing disagreement.

SPOILER:

In the novel, in the scene where the "boiler inspectors" try to shake down Vito, he tells Sonny to handle it. It was a kind of test for Sonny because Vito was "considering making Sonny his underboss."

True enough TB. But "as" is quite different from "considering", right?

Also, it supports the argument that Vito had no underboss, since Vito's consideration of Sonny for that position is not referred to as a replacement for the existing underboss not does it reference any other candidates for that position.

You got to be kidding me Olivant. You want to question this too? ...