To the guys mentioning Terminator, I can't quote you for some reason, but there is a reason Skynet didn't just send back an army of Terminator's.
It's because they were all sent at the same time. The Resistance had found out about the time travel device from a deactivated Terminator and then launnched a large assault on that base for obvious reasons. As a result only a small number of Terminators were sent through to specific points in time to attempt the assassination of John or Sarah before the Reistance assault reached it. Then Kyle Reese went through and a few other Resistance soldiers before a Terminator managed to destroy the device. Pretty sure S.M. Stirling's books were canon, written before T3 came along and kinda screwed stuff up muchly.
Also, Terminator works off the principle of multiple realities. Skynet knew that it was in trouble and knew that she could create another reality in which she did in fact win if the Terminator's were successful. In another series of books the focus was placed on later in the Machine War and actually had John waging war across multiple realities after beating Skynet in their own. I don't think this series was canon but it was also written before T3 and could still technically be realistic.
It's because they were all sent at the same time. The Resistance had found out about the time travel device from a deactivated Terminator and then launnched a large assault on that base for obvious reasons. As a result only a small number of Terminators were sent through to specific points in time to attempt the assassination of John or Sarah before the Reistance assault reached it. Then Kyle Reese went through and a few other Resistance soldiers before a Terminator managed to destroy the device. Pretty sure S.M. Stirling's books were canon, written before T3 came along and kinda screwed stuff up muchly.
Also, Terminator works off the principle of multiple realities. Skynet knew that it was in trouble and knew that she could create another reality in which she did in fact win if the Terminator's were successful. In another series of books the focus was placed on later in the Machine War and actually had John waging war across multiple realities after beating Skynet in their own. I don't think this series was canon but it was also written before T3 and could still technically be realistic.