In each Terminator movie, Skynet sends machines to kill John Connor, either directly or indirectly. Each time Skynet sends a cyborg, it does that at a later date than the time before.

If Skynet has a time machine and can travel through time, Skynet shouldn't care about a timeline and simply try to develop and use the ultimately successful cyborg killer and send it back to the time where Kyle Reese and the T-800 first traveled back in time (or even before Kyle Reese and the T-800 showed up… for example to a time where Sarah is 4 years old and unable to correctly fire a gun).

What stops Skynet from sending later and better cyborg versions back to the same time they sent the first terminator (or even earlier)?

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    SkyNet shouldn't care about a timeline - Sorry, but why do you think that? Surely SkyNet would make a point to avoid doing things that would negate its existence, or change things.
    – Zoredache
    Commented Sep 12, 2013 at 8:11
  • @Zoredache I already explained why they shouldn't care: SkyNet has time travel technology available and uses it frequently (at least once each movie). Also, your line "Surely SkyNet would make a point to avoid doing things that would negate its existence, or change things." doesn't really fit the movies because if what you write would be true, SkyNet would avoid sending T-800 back in time in the first place. In T1, T-800's mission is to kill Sarah Conner — which would change things to the positive for SkyNet. Even as T-800 fails, SkyNet gains quicker development (due to the salvaged parts).
    – e-sushi
    Commented Sep 12, 2013 at 8:23
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    I strongly object to the idea that Skynet wouldn't care. You don't explain why you think that. You just assume that it would be the case since the outcomes we witness in the story didn't have a huge impact on Skynet/Macines. My guess is that it would care a huge amount and expend huge amounts of compute cycles trying make sure it traveled to a specific time that would improve the situation for the machines and have a the least amount of risk for making things worse. Skynet is a computer after all, shouldn't we expect rationality?
    – Zoredache
    Commented Sep 12, 2013 at 8:34
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    I remember typing up something in another question that would (possibly) answer this, but can't find it at the moment... It had to do with theory (based on TSCC) on how the timelines actually worked in the Terminator universe
    – Izkata
    Commented Sep 12, 2013 at 11:06
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    Your idea was picked up in genisys if I look at the trailers. :-)
    – Hothie
    Commented Jul 3, 2015 at 7:30

6 Answers 6


It wouldn't have mattered if they had. Nothing they could have done would change anything. Notice that skynet's attempts to change the past failed. We know this because when skynet sent the terminators back to kill sarah/john, they did so because John was kicking their ass. This gets into paradox territory, so bear with me. If they had managed to kill Sarah & John, then they wouldn't have had to send anyone back, so they wouldn't have done so. But, if they didn't send anyone back, then John would survive and kick their ass, prompting them to send someone back.

Skynet's flaw was that it didn't realize that you can't change the past. Indeed, Skynet created John Connor by sending the first terminator back to kill Sarah. Remember that the resistance sends Kyle (John's best friend) back to protect her. He and Sarah end up... "getting it on" so to speak, and thus John was created. Had Skynet never sent the first terminator back, John would never have existed. The events that have happened in Skynet's "present" have happened, and cannot be changed.

Now, as for why they didn't send more back, they don't send more back because they didn't originally. It's less of a "why didn't they do this" situation, and more of a "they didn't do this".

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    Having been thinking in terms of causal timelines, time travel paradoxes, and Skynet's different futures in the several movies, and now reading your answer... it actually seems logic to me now. Thanks for helping me wrap my brain around this one. [+1 and Accepted]
    – e-sushi
    Commented Sep 12, 2013 at 14:50
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    If Skynet really wanted to change the past, it would just send back a Terminator to the '60s with instructions on how to create a safe, effective hormonal birth control (like we have now). Then Sarah would have been on the pill.
    – Jeff
    Commented Sep 12, 2013 at 15:04
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    Skynet's flaw was that it didn't realize that you can't change the past. But the past was changed by: Skynet created John Connor by sending the first terminator back to kill Sarah, so sometimes you can change past and sometimes don't ?
    – jsedano
    Commented Sep 12, 2013 at 15:09
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    @anakata no. Nothing was changed. Note that John Connor existed when they sent Arnold back in time. Had they not sent the terminator back, John would not have been born. But, he WAS born, therefore they sent the Terminator back. realize that John's existence means that the Terminator gets sent back. It is literally impossible for those two events to be separate. John's father was sent back in time to protect Sarah from the Terminator. It's a closed loop. This event happens. There is no point where it doesn't. Nothing was changed ever.
    – acolyte
    Commented Sep 12, 2013 at 15:13
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    The future changed in Terminator 2 because Judgement Day didn't happen in 1997. The first John Connor could have had a different, unknown (or perhaps coincidentally also named Kyle Reese) father. Commented Oct 8, 2014 at 14:25

Skynet was losing the war. Sending back Terminators to try and change the outcome of the war was a last ditch effort. As such, Skynet probably couldn't afford to wait until it had developed a newer, more powerful terminator.

Not to mention, the T-1000 (Terminator 2) was an "advanced prototype" (according to the T-800/101), implying it hadn't even been tested in the field before being sent back. That is a sign of desperation in itself.

In T3, we learn that Skynet was delayed (not stopped entirely). But this also meant that Skynet started with more of a leg up than before. It had the time and the resources to develop better assassins (the T-X).

However this was a different Skynet to the one originally under development (Skynet 1 had a central control point, Skynet 2 was a distributed application in cyberspace). Why is this important? Because Skynet 2 didn't know about the earlier failed plans and therefore couldn't know to send back better Terminators for reinforcements. It originally sent back the T-X to take out John's lieutenants, as John was off the grid and couldn't be found. (It was only by pure luck that the T-X found John).

In conclusion, Skynet 1 didn't send reinforcements back because it was losing the war and either didn't have any, or lost control of the time-travel apeture too quickly, and Skynet 2 didn't send reinforcements back because it wasn't aware of the earlier assassination attempts, and couldn't find John anywhere as he was off the grid up until the events of T3.

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    Yes, Reese makes it pretty clear that pretty much the humans burst into the inner sanctum of Skynet just in time to watch the original Terminator make the jump. It was extremely experimental technology- there wasn’t the TIME for Skynet to do more. T2 fudges this a little bit but not contradictorily so (after Reese went through, they may have discovered that the T-1000 had gone through and needed to come up with a new last-ditch effort). And on and on- this answer does a great job explaining how a fairly complex timeline worked with logic. Well done!
    – Broklynite
    Commented Sep 3, 2019 at 20:51

WRT the first two films:

Skynet had almost no records of 'our' time period, they could not send Terminators back to when Sarah was 4 or when she was heavily pregnant etc as they did not know where she was and they did not have the resources to just guess. Aiming for Sarah and John when they did was as much as they could do.

The reason the terminators were sent back at different times was to maximise the chance of one of them finding the target. Skynet was not expecting the resistance to capture the equipment and be able to send back bodyguards hence this did not factor into the plan.

Without the guards being sent back both prongs of the plan would have worked. Sarah would have died in the nightclub and John would have been killed as he ran through the back of the arcade.

I am sorry but I am unable to comment much on the last two films as I watched them once a few years ago so I would rather not guess. Hopefully my answer helped a little!

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    The question is about why didn't a later Skynet send another Terminator to back up the one sent after Sarah (I think)
    – Izkata
    Commented Sep 12, 2013 at 11:03
  • @Izkata Correct… that's exactly what I'm trying to find out. After the first T-800 was send after Sarah, Skynet must have been - at least - aware of that initial T-800 mission and it's (wrecked) outcome, since the whole event is a main part of Skynet history (according to T1 and T2, the salvaged T-800 remains pushed the whole Skynet thing forward). Logic would imply that Skynet would be able to come up with better strategies and/or build more advanced technology and try another trip back to the same time-coordinates where it knows it successfully "contacted" Sarah (while failing to kill her).
    – e-sushi
    Commented Sep 12, 2013 at 13:36
  • @e-sushi, sorry for the delay. Some kind of issue was preventing me from posting comments! Anyway, you're welcome! :-)
    – Stefan
    Commented Sep 17, 2013 at 13:50

Pure speculation but maybe Skynet only has a limited number of units available to send back in time. It's possible that Skynet perfected time travel at a remote research outpost that only had a few combat units assigned to it.

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    According to this page, the first movie's T-800 was sent by the prototype facility before the humans took it over and used it to send back Reese, but as Skynet kept altering the future timeline to improve itself, it was able to send back multiple units from a different future. Commented Oct 8, 2014 at 14:43

In the novelization of T2, it is stated that Skynet sent back the two Terminators

moments before the resistance managed to shut it down.

It simply didn't have enough time for more.


There are two possibilities, one, the "place" in the vector of time can only be accessed once, so they can only send terminators in different years. Two, they sent the terminators back in time to kill John Connor, but they also killed many other people that where important while they tried to kill John. if they killed only John Connor, another person would take his place.

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