I know that Sonny is well liked here in the boards (hell i liked Sonny myself)but i might get flamed for what i am about to say.
But i think that every damn move he made was out of pure instinct, he was stupid to a degree, never thought long term, Sonny should of stopped taking things personal, it is all business with the mob never personal, never.
Even i could teach Sonny a thing or two about the mob, even though i never had first hand experience i think that i would of been comparable to Michael, and Michael was not so clever when you think about it, he did have a temper streak in him but not as bad as Santino's.
Sonny wasn't totally stupid. He made a very wise, strategic move in sending Fredo to Vegas after Vito was shot. Fredo suffered an apparent nervous breakdown. With the family at war, Fredo would have been, at best, a distraction to Sonny and Tom; at worst, a very vulnerable target for the Corleones' foes. By sending him to neutral Vegas, under Don Francesco's protection, Sonny removed a serious danger to Fredo and to the rest of the family. He also "planted a flag" in Vegas by putting Fredo in with Moe Green, whose casino the Corleones had bankrolled. It's one thing to finance a casino, another to have your brother inside.
Sonny really wasn't stupid at all. It was his temper, his passion and his love for his family that many times clouded his judgement and caused him to err in some of his decisions. But he was NOT stupid.
As Turnbull pointed out, Sonny made some good moves, one of them being the way that he protected his brother, during a time of war, by sending him out to Las Vegas under the protection of the West Coast family and at the same time having his brother"inside" the Casinos and Hotels that his family had bankrolled and eventually would take over. And although it is not mentioned in the movie, let's not forget that in the book, it was Sonny who successfully commandeered a war many years earlier.
As for your view of Michael not being so clever, I must disagree with you. In the end, personal family aside of course, it was the Corleone
FAMILY who came out on top! It was Michael who was the one pulling the strings.
