The original unaltered timeline
Notes on Chronology 1
Very little of this original unaltered timeline remains. One astounding fact is that there is no John Connor. As Kyle is John's father and Kyle has not yet been sent back, John is never conceived. This requires that Sarah is the one to rise to leadership of the resistance. We know this because a T‑800 is sent back to kill her. This is true even in Terminator, though the reason we are given is that it is trying to prevent the birth of John.
We do not know when Cyberdyne develops Skynet. In Judgment Day we see that Cyberdyne's work developing the technology results in Judgment Day occurring in 1997. However, this date is dependent upon Cyberdyne receiving the chip from the crushed Terminator. As Miles Dyson says
... it was scary stuff, radically advanced. It was shattered ... didn't work. But it gave us ideas, it took us in new directions ... things we would never have thought of.
All my work is based on it.
Here they do not have the chip and so Skynet and Judgment Day must occur later than 1997.
In Rise of the Machines we see that CRS develops Skynet and Judgment Day happens in 2004. However, they are using Cyberdyne's patents, patents based upon research done on the chip. So, in this Chronology, Skynet's creation must certainly occur later than 2004.
It is interesting to note that the Sarah Connor we come to know at the beginning of Terminator becomes the leader of the human resistance without any external forces driving her: no Terminators trying to kill her, no Kyle telling her about her exploits in the future. It would be an interesting story to see how the waitress at Jeff's Big Burger develops into the leader of the human resistance.
As there is no John, Skynet's motive in sending the T‑800 back must be only to kill Sarah.
It has been suggested elsewhere that Sarah conceives John by a different father in this sequence. We reject this. It would require us to believe that this other John, without being given knowledge of his future as the leader of the resistence, without Sarah taking him underground and preparing him, without any knowledge of Terminators or the War, still rises to the exact same leadership role as the John Connor fathered by Kyle. Two entirely different men raised in completely different circumstance, with vastly different knowledge, both become the great John Connor. This is simply too difficult to accept.
However, looking at Sarah we can believe that she could rise to this role. Watching her in the deleted scene from Terminator where she is almost jumping with energy as she argues with Kyle that they should blow up Cyberdyne and end the war, this woman we believe could rise to the leadership role. In Terminator in less than 24 hours she has already accepted the reality presented to her, come up with an agressive solution, is giving orders to Kyle and, most importantly, destroys the T‑800 by herself even though she is wounded.
So we repeat, in these Chronologies before the arrival of Kyle, there is no John Connor, Sarah rises to leadership of the resistance and the T-800 is sent back to kill her.