Operation Chrono was a battle in The War Against the Machines in 2029. It was during this battle that the Resistance, led by John Connor, won a decisive victory against the machines by smashing Skynet's defense grid at its central core in Cheyenne Mountain, Colorado. It was during this time Skynet decided that instead of terminating John Connor in the present, it can terminate him in the past, starting with killing his mother, Sarah Connor by sending a T-800 to 1984 do the job, and then a T-1000 to 1995 to kill a younger version of John in case the T-800 failed to complete its own mission. Once John found out about it, he too decided to send two of his own soldiers back through time: Kyle Reese to protect his mother, and a reprogrammed Series 800 Terminator to protect his younger self.