John Connor , the son of Sarah Connor and Kyle Reese , is the leader of the worldwide human Resistance , as well as a more specialized Techcom during the War against Machines . Skynet, the main supercomputer of the machines, decides that John Connor is the center of the rebellion, and his elimination will put an end to the opposition. After repeated failures in destroying John during the war, Skynet decides to use a time travel device to send terminators to different points in the past.