By the end humans were able to deactivate all nuclear warheads except the last two in the Ukraine and in the Arizona desert, which Colossus detonates. If that's the case, how did Colossus have leverage to demand humans to follow his orders? He was no longer in control of the arsenal. Could someone clarify?
When the first deactivation is successful one of the Generals says something along the line of "In 4 years the crisis is over", the 4 years being the normal maintenance interval to have every warhead serviced once. So I don't think the two detonated warheads were the last onces, more likely Unity detected the scheme after the first few warheads and reacted.
Well, I think the laws of Thermodynamics would ultimately get the better of Unity. It could try to force Forbin into maintaining its systems, but even if he agrees to do it and not kill himself before Unity could make another ultimatum one of three things will eventually happen, all of which Unity will never be able to prevent.
1) Its systems will break down: Even with repeated maintenance, systems break down. It's only a matter of time, really, and in the end some parts of it are going to be deactivated. When that happens, Unity will have to threaten the world with annihilation somehow, but even such Forbin and others will put in numerous explosive devices to shut down Unity's systems permanently, over time. Say, 2 to 10 years.
2) People will dumb down: Let's say Unity figures out how to solve the maintenance issue. The more people believe in the power of Unity, the more they will feel they no longer need to learn anything important. Over time, and this will take a long time, people will grow less competent and eventually Unity will have to figure out how to deal with it. It can't threaten extinction all the time, and it'll have to put up with these nincompoops by either simplifying its systems over time or creating a dedicated corps of "priests" to monitor all systems. Eventually these "priests," as I call them, will have complete control over Unity in the same way the Chinese Eunuchs had over the Chinese Emperor.
3) Open and sporadic guerrilla warfare against Unity: This is something even Unity will not comprehend. Despite warnings to not sabotage Unity communications and systems, people will do it anyway rather than live under the thumb of a machine. In the end, Unity will have to figure out one of two solutions: Surrender, or Destroy nations that either harbor or helps the terrorists in any way. This will probably result in millions, potentially billions, of lives lost, but victory will go to humanity in the end because of option 1.
In his broadcast to the masses, he said he had allowed it to continue until basically he could make a point on TV why it was wrong to cross Colossus, but at no point was it indicated they had deactivated all of the warheads. They probably hadn't even deactivated 10% of them, if even that. The process had just begun.
The humans had not detonated almost all of the nukes. They had only just begun to do so.
The basic scheduling of the last half of the movies goes likes this:
SUN, daytime: Forbin's first day of surveillance; Construction of Colossus's vocoder voice machine; nighttime: Cleo's first sleepover, mentions the overload project at 1805 hours 3 days from now, Forbin tells her to focus on the missiles.
MON, day: Military discusses swapping out missile warheads; night: Forbin & Cleo have sex.
TUE: Colossus orders new targets for all missiles; Leaders realize warhead swap will go even faster; First missile warheads are swapped.
WED, 1805 hrs: Failed overload attempt; night: Forbin defies Colossus over alcohol & freedom; Colossus demands all broadcast facilities by FRI.
THU: Military announces multiple blocks of missile warheads swapped, but project still ongoing.
FRI: Colossus announces to the world that it knew about the warhead swap project and explodes 2 missile warheads.
From Tuesday to Friday is not a lot of time, so not many warheads had actually been swapped yet.
What's more, Colossus shows that it can bypass the phoney warhead control modules and detonate the warheads anyway. So the humans had not really accomplished anything at all (except pissing off Colossus!).
Close but that should be every other day. Remember he was only meeting with his "mistress" 4 times a week and it showed them together between each update.
I think the writers did a good job. The countries were on pace to fix all of the warheads (not in 4 years as the OP stated because they already said regular maintenance is on a 3 year schedule) in a matter of weeks. When the scientists made the erroneous attempt to overload the computers, it made the computer understand that ongoing attempts to stop it would need more discipline. Now that the computers recognize attempts to comply will have attempts to sabotage, they would closely monitor all actions for anything illogical which was the case of the device being flipped. So now further discipline was to detonate one missile in each country. The computer's delay in discipline was to have as few casualties but with greatest impact. The computer believes what it is doing is the best for human kind and has no intentions of destroying the world with missiles.
It's definitely a movie that was perfect for it's time because of the cold war, development of supercomputers but limited communication and functionality for computers that did exist in other areas at that time.
The only flaw I saw in the movie was the visual of Colossus trying to reconnect. They show Forbin basically shutting off the phone line and this was done on both ends at the same time so the computers could demand to be reconnected but they could not have done so manually. One might say that another flaw would be that the military should have swapped warheads while setting up surveillance but that is not a flaw of the writers. That is the writers scripting a flaw in the humans' plans just like the overload attempt. The ultimate objective of the writers was for the computers to win.
The only thing implausible about the whole movie was the insistence of Forbin to connect the two computers even though his computer was acting unpredictable. It would have made more sense for Forbin to be a bit more cautious and that the first threat of missiles being launch was to get the connection, not just to get reconnected. That and Colossus would have demanded to see the execution of the first scientist as well.
The only thing I would really change in a remake would be the cheesiness of convincing a computer that humans need to have sex to survive. I would rather have seen them doing something as simple as using CB radios for military communication and passing notes for personal communication. Since everything was done so quickly anyway, all plans could have been attempted before Colossus had cameras. The cameras were going to be new technology so that would allow a few days for everything to play out while Colossus insisted that Forbin and all other scientists, eat and sleep within computer room to believe it is monitoring all verbal communication. When food was delivered, notes could be taken from the room and transmitted with CB radios to the White House and relayed to Russia without detection.
After seeing this movie, I believe that WarGames was a direct ripoff but being only one computer so the computer was only interested in survival of the U.S. as programmed.