Describe Oceania in Winston's childhood

In Ninety Eighty-Four (1984) novel by George Orwell, as Winston remembers his childhood days, he thinks of Oceania’s bond to the other nation of the world, the Eastasia and Eurasia. Based on official documents, Oceana has an alliance with the Eastasia, and have Eurasia as their enemy. However, thought that the data are modified and changed.