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human
[Terminator] Question about the use of time travel and the origin of Skynet

If Skynet and the Terminator models are reverse engineered from the remains of the T-800 from the original movie where does the original design or concept come from?

If Arnold succeeds in killing Sarah Connor or kills Kyle Reese befoe John Connor is conceived then in the future there will be no need to send Arnold back to kill anyone and there will be no T-800 remains to base any of Miles Dysons work on and Skynet never gets built.

Is there any way to piece all of this together and have it make sense?

Also why do none of them, including Skynet, seem to be aware that if they are successful in preventing their enemies' from existing they also prevent their own existence?


Edit: I just noticed there's another similar post from less than a day ago.
gpt
The first three terminator movies occurs after various iterations of skynet is defeated in the future, and seeing that its defeat is iminent, skynet then attempts time travel to change history.  This destroys its original timeline, but creates a new timeline where an alternate skynet may succeed.

**Timeline 0:**  Skynet is created through normal means, judgement day happens, but skynet is defeated by John Connor and a number of his friends.  Skynet has however developed time travel and sends a T-800 back in time.  John Connor sends Reese back in time to stop him.  This time travel creates timeline 1 (timeline of Terminator 1).

**Timeline 1:**   In this timeline a number of John Connor's friends are assasinated by the T-800, and John is concieved by the future Reese, rather than whoever Sara Connor would have slept with normally.  in the original timeline Reese was *not* John's father.  T-800 is defeated, and Sara begins a strange new life.   Using the destroyed T-800, Cyberdine gets a leg up on developing skynet.  This skynet duplicated the judgement day of the original, but this timeline John Connor has recieved additional training and experiences and is once again successful in defeating skynet.  Skynet has still had time to develop time travel and so seeing its defeat, it sends the T-1000 back in time.  Alternate John Connor chooses to not send Reese back (likely there is no Reese in this timeline), but to send back a reprogrammed T-800.  This creates timeline 2, which begins with Terminator 2 movie.

**Timeline 2:** In this timeline, cyberdine systems is heavily damaged by the T-800 and Sara Connor, and much of the research is lost.  Their main programmer is also killed.  But enough information is left that the military recreates Skynet *again* at their base.  This skynet causes judgement day, but is again defeated by John Connor in the future.  Skynet-2 has still devleoped time travel, and so it sends back the female terminator, and the resistance sends back another T-800.  This creates Timeline 3, the events of terminator 3.

**Timeline 3:**  In timeline 3, John Connor and the terminator rescue his future wife, and take her to the military base, in an attempt to destroy skynet.  They are too late, and judgement day occurs, but this time John and his future wife end up in a very defensible bunker where they once again lead the resistance.  This leads to terminator 4, which is a continuation of Timeline 3.  In this movie we do not see skynet defeated, so we do not know if it has developed time travel and will once again alter time if it loses.

The key thing here, is that skynet knows each time it sends a terminator back, its destroying its own timeline.  So it only does so when it knows its lost.  Skynet considers *any* alternate timeline where a different skynet defeats humanity to be an acceptable solution, but only if it has no chance of victory in its own timeline.