Skynet was a computer system developed by the defense firm Cyberdyne Systems for the United States Armed Forces. Skynet was first built as a "Global Digital Defense Network", given command over all computerized military hardware and systems, including the B-2 stealth bomber fleet and America's entire nuclear weapons arsenal. The strategy behind Skynet's creation was to remove the possibility of human error and slowness of reaction time to guarantee fast, efficient response to enemy attack.

In the Terminator storyline, Skynet was originally installed into the U.S. military mainframe to control the national arsenal on August 4, 1997. On August 29 it gained self-awareness[1] and the panicking operators, realizing the extent of its abilities, attempted to shut it down. Skynet perceived the attempt to deactivate it as an attack and came to the conclusion that all of humanity would attempt to destroy it. To defend itself, it determined that humanity should be exterminated.

Before it could be deactivated, Skynet launched the US nuclear missiles under its command at Russia, to which Russia responded in kind by firing many of its nuclear missiles back at the United States and its allies. As a result of the nuclear exchange, over three billion humans were killed in just minutes. Governments around the world collapsed and anarchy descended.

During this time, Skynet used its remaining resources to gather a slave labor force from surviving humans. These slaves constructed the first of its automated factories, which acted as the base for its agenda. Within decades Skynet had established a global presence and used its mechanized units to track down, collect, and dispose of the human survivors.