November 2nd, 1985 is the day that almost half of New York was destroyed by the sudden appearance of a giant Alien Squid. The prospect of extraterrestrial invasion caused both the American and Soviet governments to reconsider the escalating conflict of the Cold War, and brought about a new age of peace and prosperity.
What nobody but Dan Dreiberg and Laurie Juspeczyk knew, however, was that the alien was, in fact, a horrible cloned monster, created by Adrian Veidt, specifically to end the tension between the US and Russia. Rorschach was killed by Dr. Manhattan before he could get back to civilization, so Ozymandias' terrible secret was safe, for one whole year.
Because of the return of heroes such as Nite Owl and Silk Spectre, many civilians attempted to create their own costumed identities. Only few chose to become vigilantes. Although many of these new heroes and villains were novices and weak, some of them became lasting characters. This mask boom caused the government to enforce the Keene Act with their Watchmechs.
Within the weeks following the attack, radical Right-Wing newspaper the New Frontiersman published an article allegedly taken from the journal Rorschach left before traveling to Karnak. Though the journal had clear evidence that the attack was a scam, the article was overlooked. It did cause Veidt to grow paranoid, however, and hastened his development of the Hall of Souls.
Exactly one year later, on November 2nd, 1986, Adrian Veidt, newly elected President of the United States, discovers thanks to the Bucket of Blood hallucination that one of the other alternate realities actually did have Alien Squid in it, abandoned creations of Dr. Manhattan that had begun to breed and that they were soon going to attempt to break into our reality.
With the help of the GSA, Veidt manages to placate the alien queen, and save the world a second time. What he fails to realize, though, is that the aliens now possess Earth technology, and begin working on the weapons that would appear later in the Robot Invasion arc.