1984 World RPG

takes place in an imagined future in an unspecified year believed to be 1984, when much of the world is in a state of perpetual war. Britain, now known as Airstrip Number 1, has become a province of the totalitarian superstate called Oceania, which is led by Big Brother, a dictatorial leader backed by an intense personality cult manufactured by the Thought Police. The party promotes omnipresent government surveillance and, through the Ministry of Truth, historical denial and constant state propaganda to persecute the individuality and independent thinking of citizens

INGSOC, which stands for English Socialism, is an ideology founded on and based primarily on the British Isles. It reflects many other totalitarian political ideologies and, in the political compass, lies on the border between extreme right extremism and extreme left extremism.

The protagonist of 1984, Winston Smith, mentions not having heard the word INGSOC before the 1960s, but having heard of English Socialism in the 1950s. This at least allows us to restrict its foundation to sometime within 50 years. Oceania was probably not founded under INGSOC, as several points in the book seem to directly point to or mention a civil war in the country. No details are given and it's not even said if INGSOC was involved, but it's pretty safe to assume that's what brought INGSOC to power.