Know what I never understood? Why didn't the humans just use the time machine to go back in time to when the time machine was first invented, destroy it then, so then they couldn't send any terminators after John and his mom in the first place, and any terminators already sent would...
oh, wait...
Well, ordinarily any of the actions in these films would have created a huge temporal paradox. I.E. If Skynet succeeds in preventing John Connor from growing up and leading the resistance, then why would Skynet send Terminators into the past in the first place.
If terminators are never sent back through time, the wreckage of the first terminator is never found and never used as the basis for Skynet's creation which in turn leads to the creation of the terminators and Judgement Day.
If terminators are never sent back through time, Kyle Reese is never sent back through time to protect Sarah Connor and become John Connor's father.
But this is all explained by a theory of time travel that states that the events of the movie is how the time line was fated to progress from the get-go, so in fact the future is never changed from its original path, it only appears that way to people living at various points in the timeline.
The other theory is called the N-Jump theory that states that although it may appear that John Connor's and Skynet's existence are pivotal for each other's creation, since Skynet would not need to send a terminator back through time to kill his mother or him had he not grown up to be the leader of the Resistance, and at the same time not spawned its own creation as a result, Kyle Reese would never have been sent through time and fathered John Connor.
The N-Jump states that although the end result in the timeline is the same, I.E. Judgment Day, the events leading up to it, prior to any time-traveling taking place, would have been different. I.E. John Connor's father, whoever he was, was just some guy living in 1984 Los Angeles who impregnated Sarah Connor and died before Judgement Day, and Skynet was developed by Cyberdyne systems through normal technological progression without the kick start from the recovered terminator wreckage. (A deleted scene from the first movie shows that the factory where Sarah crushes the terminator in an aluminum press is in fact a
Cyberdyne manufacturing facility, and of course, we see what happened to the first terminator's remains in the second movie.) However, when the Terminators and the various protector figures were send back through time. The timeline was slightly altered, but still had the same ultimate outcome.
Another mystery of the movie is who authored the "No fate but what we make for ourselves." speech. Every character in the movies thusfar who recites it learned it from someone else. Kyle Reese teaches it to Sarah, who teaches it to John Connor, who teaches it to Kyle Reese. It's a paradox. Assuming that the original timeline, prior to any time traveling by terminators or protectors. was different from the way it is in the films, then someone had to have been the original author of the speech, presumably John Connor, since Kyle tells Sarah he learned it from Connor, and recites it to her prior to John's birth, AND they haven't conceived John yet, succeeded in killing the terminator yet, nor has the terminator succeeded in killing Sarah, which means that the original timeline is probably still intact at that point. In the "new" timeline, where the various time-traveling antics occurred in the various movies, the speech appears to have no author, but rather always existed, (though I have my suspicions that the speech will come from another character in this new movie, and though Connor will remember his mother telling it to him as a child, this is what will inspire him to tell it to Kyle Reese).
Of course, it's equally possible that the timeline as it occurs in the movie, including all the time "altering" shenanigans is
exactly how the timeline was fated to progress from the get-go. But that would mean that the speech was a complete lie. My head hurts.
