The Oceanus-Gorgon Empire was an autocracy jointly ruled by Oceanus the leader of the Legion and Gorgon leader of the Splicers formed in 1975 after the Legion-Splicer Treaty. The new order successfully conquered most of Rapture. However they were opposed in small opposition by the alliance of Big Sisters and Big Daddies not wanting another tyrant to rule Rapture and aided by a group of Splicers that refused to act as hosts to The Legion (which was part of the treaty) who were being purged by Gorgon and his Legion-Splicers in a civil war. These conflicts reached a climax on the New Year of 1980 with Oceanus and Gorgon seeing the new year as the destruction of all of their enemies and the beginning of there new order in Rapture knowing that there enemies were planning a large scale attack on them which they prepared for.
The Battle for New Year as it would be known began when the Big Sisters and Big Daddies and Splicers lauched the first strike at the Imperial Plaza where Oceanus and Gorgon ruled over there Empire. For the first half of the battle the two tyrants had the upper hand easily destroying a signifigant amount of enemy forces singlehandedly. However their enemies retaliated using the non-muant Splicers as willing distractions for the Big Sisters and Daddies to launch a counter-attack against. Oceanus was killed in the conflict by a Big Daddy that died shortly after from wounds inflicted by Oceanus. Gorgon fled the battle after Oceanus' death into the Legion's main hive where he planned to release a deadly virus he created as a last resort to win the battle known as the Blue Pandemic. A group of Splicers wanting revenge for Gorgon's purge of them followed him to the Legion hive and detonated a small nuclear bomb they carried with them sacrificing themselves along with killing all of the Legion-Splicer hybrids, nearly eradicating the Legion and killing Gorgon as well. However Gorgon was able to release The Blue Pandemic virus on Rapture before being killed by the bomb. With the deaths of Oceanus and Gorgon the Empire lost the battle and fell but not before releasin a terrible disease that wiped out 40% of Rapture's population before becoming concentrated in one area.