you guys as Steel, knightwolf68, and illustrator are wrong!!!!
In my theory or probably fact,
In the past, present, and future, John Connor didn't meet his father, Kyle Reese who happened to be an excellent soldier. In future, Machines tried to kill Kyle but it’s hard to kill him. Not only that but Machines cant find john Connor who has been hiding anywhere for years as he is non- exist (according to T-3 storyline) So Machines decided to send a terminator to kill Sarah Connor( which is easier than killing Kyle) in the past.
Because in my theory the machines are responsible for John Connor's existence and were the creators of their own demise
the human resistance sent Kyle to the past to save Sarah who was not pregrent. After a solider and Sarah had having sex each other and then Sarah was started pregrnt who happened to be john Connor after john's father the future died in T-1. You guys remember!!!
Kyle was the one who reshaped the Future by changing the Past because Kyle was the one who knows the machines almost destroyed all humans in future even Kyle tried to kill all machines since machines created improved and smart terminators. Not only that but Kyle knows john needed more time to build his own terminators and start war against machines in the future ( T-4 probably)
Have you noticed that John's own terminators that sent to the past to SAVE Sarah (t-2)? And Kate also sent another terminator with same programmer to the past to save younger Kate and john (used to be girlfriend/boyfriend after T-1 and before T-2 according to t-3 storyline) because Machine tracked and found young john in the past who started building his own terminators. That why Machines created a better terminator called T-X (Kristen the actress) and sent to the past and kill younger Kate, john and their crew (t-3).
According to t-2, a good terminator with John found Sarah in the ward. When she saw terminator and knew john the future is alive and finally builds terminators of his own against machines.
After t-2, Sarah explained everything to john and decided to separate way for good. So Sarah, the future wrote a will ( in case she dies) for terminator because she knows more about the future. So u guys see t-3 movie. It explains everything. How did Sarah know then? As I said Sarah is not dead and has been hiding somewhere like john did. John was shocked because he thought his mother died.
If u guys don't understand my grammars, I am sorry that's the best I can.