WARNING: "Godfather" spoilers below
The drapes question has been debated to death, there's no confirmed answer unless it was mentioned in one of those later GF novels i dunno haven't read those. The three main suspects are Fredo, Al Neri and Rocco. Personally i rule out Fredo right away. Fredo didn't want to harm Michael he loved him, he just felt he had been passed over being the older brother and he felt Michael wasn't giving him anything to do, and that he was always treated like the idiot of the family. So he tried to get into business with Roth to get something for himself, Roth obviously used him correctly deducing that he was dumb and an easy way to get to Michael. There's only two ways it could have been Fredo either he was planning on having Michael killed and all the later stuff he says was lies to try and save himself which would change the whole film, but it's clearly not that because after the attempt we hear Fredo say to Johnny Ola on the phone "you guys lied to me". Obviously they had told him Michael would not be harmed and naive Fredo believed them. The other possibility is that Fredo was so dumb that he left the drapes open without figuring out what it was for. That is a possibility it's consistent with Fredo's character although it turns him from dumb and naive into practically braindead because how could you not know what's that for and what could they possibly tell him that would be a plausible lie? I hate that possibility which plays into me ruling Fredo out but the main thing is i think the film more or less tells you who it is just never completely confirming it.
So it's either Rocco or Al Neri, i believe it's the former. Both had the opportunity but there's three main things that i think points to Rocco. After the hit Michael orders Rocco to keep the assassins alive, he then talks to Tom Hagen who brings up the possibility of either Rocco or Al being involved, Michael then says one thing he learned from his dad was to try and think like the people around him, he also mentions that the men who works for him are first and foremost businessmen which i think is clearly saying he believes either of them would think of Michael's assassination as a business decision so it could be either. The thing that he says about his dad in my opinion is referring to Part 1 when Vito tells him whoever comes to you to set up the peace meeting with the other bosses is the one who has betrayed you, that's obviously Tessio and we know it was Tessio he admits it to Tom before he is taken away. Interestingly Tessio says it was just business and of course one of Michaels most famous lines from the first one is "it's strictly business", showing these guys are thinking the same about each others potential murders. Well i think the test Michael was setting there was whether the assassins were brought to them alive or not, if they were then they'd get it all out of them, if it was Rocco he'd not want to bring them alive and obviously they were killed; i think Michael figured it was Rocco then when they were killed. He failed the test. A problem with that is of course that he keeps Rocco alive, there's a few explanations for that. One is Michael wasn't in the best place immediately following this, he could have figured that killing Rocco could result in his men defecting to Roth. He also might have thought Rocco would stay in contact with Roth so he'd keep tabs on Rocco without letting on he knows and could possibly get to Roth that way. That explanation works particularly well with how long Rocco is kept alive afterwards as of course he would wait until the heat died down before trying to contact them. Then there's Roth's assassination. It's a suicide mission and Rocco is a Captain, you'd figure he'd pay some nobody to do it but instead he sends one of his best men, perfect machiavelian move because Roth would die and so would Rocco in a way that would absolve Michael of blame for it as he didn't kill him. If anything it could make those who were loyal to Rocco more loyal to Michael as they saw Rocco make the ultimate sacrifice for him. Now the problem with that is of course why on earth would Rocco go on a suicide mission. My explanation for that is that when Michael mentioned it to him he figured out Michael knew and he basically had no choice. His other options are flee, kill Michael or become an informant. With the latter he saw what happened to Pentangelli and he obviously knows that Michael has anticapted Rocco attempting all of those, so if he doesn't go through with it Michaels men are ready to kill Rocco and/or his family. Killing Roth and dying himself is the best option because his family at least will be okay and it allows him to go out as some sort of mafia hero rather than a traitor.
That's why i think Rocco, i think it is the most logical and all of the pieces seem to fit, the things that aren't fully explained have plausible explanations. Although there's some that believe it was Al Neri and that theory is kind of awesome. The Neri did it one is actually my favourite of the three, but i go with Rocco because you need to do more gymnastics to make it work and Neri needs to luck into it all while it's all more straightforward to Rocco. The thing is it's never explicitly confirmed that Rocco ordered the assassins to be killed, IMO he did but it's definitely not 100%. So it's possible that either Al had his men kill the assassins or Rocco's men were secretly working for Al and they killed them for him. Al couldn't have possibly seen everything that would happen if this failed but i'm sure he'd be ready to clean up if it failed and everything fell in line. In this sense it makes Al the true successor to Vito in an odd and awesome way. The thing is Michael never truly lives up to Vito's machiavelian abilities, Part 1 is all Vito it was a gift left from him the Tessio/Clemenza thing, in Part II he's nearly killed and while in Part 1 it's confirmed everything Vito said turned out right it's not confirmed if Michael got it right with Rocco. So him failing and having an innocent man killed while making the true perpetrator one of his top men is very consistent with him not being Vito. Al either lucked into all this or he was truly machiavelian in the form of Vito having covered all bases in this situation. If it's pulled off Roth will reward him by i'm guessing putting him in charge of New York, if it fails Rocco gets the blame and one of his top rivals is taken out. The latter happens whether Al was involved or not and he becomes Michaels top man running Vegas for him at one point, pretty much becoming Roth which is the best possible situation making Al seem like some sort of genius which is awesome since he just kind of stands around or assassinates people in the films. There's more problems with this than Rocco though. For one Al is Michaels Luca Brasi, those two are the most loyal characters in the series, obviously the appeal of the theory is that Michael never inspired a Luca Brasi because he was no Vito but that doesn't actually make sense. In Part III Al is still a hitman and bodyguard to Michael he then becomes loyal to Vincent and at the end despite his age he commits the final murders Michael orders in the Vatican. Michael is on his way out in Part III then when he's brought in he is severely weakened, Al's planning of Zaza's murder was the turning point in getting Michael and Vincent back into power. If he was so dead set on gaining his own power and wasn't really loyal to Michael, why would he not take the opportunity to elimate the weakened Michael and unprepared Vincent and take over himself? I don't think that squares with the power hungry Al painted in this situation. The other option that's nowhere near as good is he made a mistake and he regretted it, when he got away with it he completely devoted himself to Michael. The problem with that (and the first one too actually) is why strike then? Michael is in just as good of a position as Roth at this point, why go with a guy you don't know well like Roth who is known for being devious and could easily renege on any promises he's offering over Michael who closely trusts you and will always have you around as one of if not his top guy? The better plan would be to wait until Michael had reached all his goals while building up your own base then take Michael out and take over. Thing is Al's intelligence is never really confirmed, he doesn't talk that much we know he was good at killing but so was Luca Brasi and he clearly wasn't smart. Some of these hinge on Al either being smart or not so smart and that's not known so that holds it all back. The other problem with this is why would Rocco go on the suicide mission if it wasn't him? If he had figured out Michael suspected him i can't see why he wouldn't protest, and if he hadn't figured that out surely he would have questioned Michael sending him to die. There's two possible explanations for that either he figured out Michael suspected him and while he didn't he thought there was no point in protesting and going through with it was his best option for the reasons i explained in the Rocco did it post, or he was just blindly loyal to Michael but that's not really part of his character that's more Al. Actually another one could be he's felt bad about the assassins being killed by his men and he figures he should make up for it with this, but that's not great either. So yeah as much as i like the idea of the Al one it's a lot more convoluted and betrays known character traits than Rocco doing it.
The drapes question has been debated to death, there's no confirmed answer unless it was mentioned in one of those later GF novels i dunno haven't read those. The three main suspects are Fredo, Al Neri and Rocco. Personally i rule out Fredo right away. Fredo didn't want to harm Michael he loved him, he just felt he had been passed over being the older brother and he felt Michael wasn't giving him anything to do, and that he was always treated like the idiot of the family. So he tried to get into business with Roth to get something for himself, Roth obviously used him correctly deducing that he was dumb and an easy way to get to Michael. There's only two ways it could have been Fredo either he was planning on having Michael killed and all the later stuff he says was lies to try and save himself which would change the whole film, but it's clearly not that because after the attempt we hear Fredo say to Johnny Ola on the phone "you guys lied to me". Obviously they had told him Michael would not be harmed and naive Fredo believed them. The other possibility is that Fredo was so dumb that he left the drapes open without figuring out what it was for. That is a possibility it's consistent with Fredo's character although it turns him from dumb and naive into practically braindead because how could you not know what's that for and what could they possibly tell him that would be a plausible lie? I hate that possibility which plays into me ruling Fredo out but the main thing is i think the film more or less tells you who it is just never completely confirming it.
So it's either Rocco or Al Neri, i believe it's the former. Both had the opportunity but there's three main things that i think points to Rocco. After the hit Michael orders Rocco to keep the assassins alive, he then talks to Tom Hagen who brings up the possibility of either Rocco or Al being involved, Michael then says one thing he learned from his dad was to try and think like the people around him, he also mentions that the men who works for him are first and foremost businessmen which i think is clearly saying he believes either of them would think of Michael's assassination as a business decision so it could be either. The thing that he says about his dad in my opinion is referring to Part 1 when Vito tells him whoever comes to you to set up the peace meeting with the other bosses is the one who has betrayed you, that's obviously Tessio and we know it was Tessio he admits it to Tom before he is taken away. Interestingly Tessio says it was just business and of course one of Michaels most famous lines from the first one is "it's strictly business", showing these guys are thinking the same about each others potential murders. Well i think the test Michael was setting there was whether the assassins were brought to them alive or not, if they were then they'd get it all out of them, if it was Rocco he'd not want to bring them alive and obviously they were killed; i think Michael figured it was Rocco then when they were killed. He failed the test. A problem with that is of course that he keeps Rocco alive, there's a few explanations for that. One is Michael wasn't in the best place immediately following this, he could have figured that killing Rocco could result in his men defecting to Roth. He also might have thought Rocco would stay in contact with Roth so he'd keep tabs on Rocco without letting on he knows and could possibly get to Roth that way. That explanation works particularly well with how long Rocco is kept alive afterwards as of course he would wait until the heat died down before trying to contact them. Then there's Roth's assassination. It's a suicide mission and Rocco is a Captain, you'd figure he'd pay some nobody to do it but instead he sends one of his best men, perfect machiavelian move because Roth would die and so would Rocco in a way that would absolve Michael of blame for it as he didn't kill him. If anything it could make those who were loyal to Rocco more loyal to Michael as they saw Rocco make the ultimate sacrifice for him. Now the problem with that is of course why on earth would Rocco go on a suicide mission. My explanation for that is that when Michael mentioned it to him he figured out Michael knew and he basically had no choice. His other options are flee, kill Michael or become an informant. With the latter he saw what happened to Pentangelli and he obviously knows that Michael has anticapted Rocco attempting all of those, so if he doesn't go through with it Michaels men are ready to kill Rocco and/or his family. Killing Roth and dying himself is the best option because his family at least will be okay and it allows him to go out as some sort of mafia hero rather than a traitor.
That's why i think Rocco, i think it is the most logical and all of the pieces seem to fit, the things that aren't fully explained have plausible explanations. Although there's some that believe it was Al Neri and that theory is kind of awesome. The Neri did it one is actually my favourite of the three, but i go with Rocco because you need to do more gymnastics to make it work and Neri needs to luck into it all while it's all more straightforward to Rocco. The thing is it's never explicitly confirmed that Rocco ordered the assassins to be killed, IMO he did but it's definitely not 100%. So it's possible that either Al had his men kill the assassins or Rocco's men were secretly working for Al and they killed them for him. Al couldn't have possibly seen everything that would happen if this failed but i'm sure he'd be ready to clean up if it failed and everything fell in line. In this sense it makes Al the true successor to Vito in an odd and awesome way. The thing is Michael never truly lives up to Vito's machiavelian abilities, Part 1 is all Vito it was a gift left from him the Tessio/Clemenza thing, in Part II he's nearly killed and while in Part 1 it's confirmed everything Vito said turned out right it's not confirmed if Michael got it right with Rocco. So him failing and having an innocent man killed while making the true perpetrator one of his top men is very consistent with him not being Vito. Al either lucked into all this or he was truly machiavelian in the form of Vito having covered all bases in this situation. If it's pulled off Roth will reward him by i'm guessing putting him in charge of New York, if it fails Rocco gets the blame and one of his top rivals is taken out. The latter happens whether Al was involved or not and he becomes Michaels top man running Vegas for him at one point, pretty much becoming Roth which is the best possible situation making Al seem like some sort of genius which is awesome since he just kind of stands around or assassinates people in the films. There's more problems with this than Rocco though. For one Al is Michaels Luca Brasi, those two are the most loyal characters in the series, obviously the appeal of the theory is that Michael never inspired a Luca Brasi because he was no Vito but that doesn't actually make sense. In Part III Al is still a hitman and bodyguard to Michael he then becomes loyal to Vincent and at the end despite his age he commits the final murders Michael orders in the Vatican. Michael is on his way out in Part III then when he's brought in he is severely weakened, Al's planning of Zaza's murder was the turning point in getting Michael and Vincent back into power. If he was so dead set on gaining his own power and wasn't really loyal to Michael, why would he not take the opportunity to elimate the weakened Michael and unprepared Vincent and take over himself? I don't think that squares with the power hungry Al painted in this situation. The other option that's nowhere near as good is he made a mistake and he regretted it, when he got away with it he completely devoted himself to Michael. The problem with that (and the first one too actually) is why strike then? Michael is in just as good of a position as Roth at this point, why go with a guy you don't know well like Roth who is known for being devious and could easily renege on any promises he's offering over Michael who closely trusts you and will always have you around as one of if not his top guy? The better plan would be to wait until Michael had reached all his goals while building up your own base then take Michael out and take over. Thing is Al's intelligence is never really confirmed, he doesn't talk that much we know he was good at killing but so was Luca Brasi and he clearly wasn't smart. Some of these hinge on Al either being smart or not so smart and that's not known so that holds it all back. The other problem with this is why would Rocco go on the suicide mission if it wasn't him? If he had figured out Michael suspected him i can't see why he wouldn't protest, and if he hadn't figured that out surely he would have questioned Michael sending him to die. There's two possible explanations for that either he figured out Michael suspected him and while he didn't he thought there was no point in protesting and going through with it was his best option for the reasons i explained in the Rocco did it post, or he was just blindly loyal to Michael but that's not really part of his character that's more Al. Actually another one could be he's felt bad about the assassins being killed by his men and he figures he should make up for it with this, but that's not great either. So yeah as much as i like the idea of the Al one it's a lot more convoluted and betrays known character traits than Rocco doing it.