One of the issues raised in 1984 is the idea that history is mutable or changeable, that truth is what the Party deems it to be, and that the truths found in history are the bases of the principles of the future. Some Fascist German leaders of the time boasted that if you tell a lie loud enough and often enough, people will accept it as truth. The Stalinists perfected this modus operandi by re-writing people and events in and out of history or distorting historical facts to suit the Party's purposes. "Who controls the past controls the future: who controls the present controls the past," runs the Party slogan in 1984.
Winston Smith's position in the Ministry of Truth is that of creating or forging the past into something unrecognizable to any person with an accurate memory (even memory is controlled in 1984) so that each forgery "becomes" historic fact. One moment, Oceania is and always has been at war with one enemy, the next moment it is and has always been at war with another, and the people of Oceania accept the information as true. It is an exaggeration of a phenomenon that Orwell observed in his own time and reported with true clarity in 1984: People most readily believe that which they can believe most conveniently.
The novel makes the distinction between truth (the actual issues and circumstances of an event) and fact (what are believed to be the issues and circumstances of an event) and then explores the social-political-ethical-moral nuances of the evil manipulation of facts in order to control individuals and societies for political gain. Orwell was concerned that the concept of truth was fading out of the world. After all, in the arena of human intercourse of which politics is a part, what is believed is much more powerful than what is actual. If the leaders of nations are the people dictating the what, where, when, who, and how of history, there can be little question that lies find their way into the history books, that those lies are taught to school children, and that they eventually become historical fact.
This concern is quite obvious in 1984. During Orwell's time as a resistance fighter in Spain, he experienced this rewriting of history first-hand: He noticed that newspaper stories were often inaccurate: There were often reports of battles where no fighting had occurred or no report at all of battles where hundreds of men had died. Orwell conceded that much of history was lies, and he was frustrated by the fact that he believed that history could be accurately written.
This "rewriting" of events is not reserved for totalitarian governments. Even in our own time, candidates for all levels of government, including those for President, "remember" things differently, and politicos nationwide attempt to put their "spin" on events that affect us all. It is as if an event can be stricken from history if the population does not remember it. And again, at all levels, non-specific or ambiguous language is used to shade or change the actual events to favor the candidates' or leaders' position or ideology. With every era, our "heroes" are disclaimed, and history books rewritten. As the culture and the ideology change, history changes. Sometimes these distortions are innocent and innocuous differences of perspective; other times, they are deadly dangerous.