<P> Some of the influences on historians, which may change over time are: </P> <Ul> <Li> Access to new data: Much historical data has been lost . Even archives have to make decisions based on space and interest on what original material to obtain or keep . At times documents are discovered or publicized that give new views of well established events . Archived material may be sealed by Governments for many years, either to hide political scandals, or to protect information vital for national security . When these archives are opened, they can alter the historical perspective on an event . For example, with the release of the ULTRA archives in the 1970s under the British 30 years rule, a lot of the Allied high command tactical decision making process was re-evaluated, particularly the Battle of the Atlantic . The release of the ULTRA archives also forced a re-evaluation of the history of the electronic computer . <Ul> <Li> New sources in other languages: As more sources in other languages become available historians may review their theories in light of the new sources . The revision of the meaning of the Dark Ages are an example of this . </Li> </Ul> </Li> <Li> Developments in other fields of science: DNA analysis has had an impact in various areas of history either confirming established historical theories or presenting new evidence that undermines the current established historical explanation . Professor Andrew Sherratt, a British prehistorian, was responsible for introducing the work of anthropological writings on the consumption of currently legal and illegal drugs and how to use these papers to explain certain aspects of prehistoric societies . Carbon dating, the examination of ice cores and tree rings, palynology, SEM analysis of early metal samples, and measuring oxygen isotopes in bones, have all provided new data in the last few decades with which to argue new hypotheses . Extracting ancient DNA allows scientists to argue whether or not humans are partly descended from Neanderthals . </Li> <Li> Nationalism: For example, when reading schoolbook history in Europe, it is possible to read about an event from completely different perspectives . In the Battle of Waterloo most British, French, Dutch and German schoolbooks slant the battle to emphasise the importance of the contribution of their nations . Sometimes the name of an event is used to convey political or a national perspective . For example, the same conflict between two English speaking countries is known by two different names, for example, the "American War of Independence" and the "American Revolutionary War". As perceptions of nationalism change so do those areas of history that are driven by such ideas . </Li> <Li> Culture: For example, as regionalism has become more prominent in the UK some historians have been suggesting that the English Civil War is too Anglo - centric and that to understand the war, events that had previously been dismissed as on the periphery should be given greater prominence; to emphasise this, revisionist historians have suggested that the English Civil War becomes just one of a number of interlocking conflicts known as Wars of the Three Kingdoms . Furthermore, as cultures develop, it may become strategically advantageous for some revision - minded groups to revise their public historical narrative in such a way so as to either discover, or in rarer cases manufacture, a precedent which contemporary members of the given subcultures can use as a basis or rationale for reform or change . </Li> <Li> Ideology: For example, during the 1940s it became fashionable to see the English Civil War from a Marxist school of thought . In the words of Christopher Hill, "the Civil War was a class war ." In the post World War II years the influence of Marxist interpretation waned in British academia and by the 1970s this view came under attack by a new school of revisionists and it has been largely overturned as a major mainstream explanation of the middle 17th century conflict in England, Scotland, and Ireland . </Li> <Li> Historical causation: Issues of causation in history are often revised with new research: for example by the middle of the twentieth century the status quo was to see the French Revolution as the result of the triumphant rise of a new middle class . Research in the 1960s prompted by revisionist historians like Alfred Cobban and François Furet revealed the social situation as much more complex and the question of what caused the Revolution is now a closely debated one . </Li> </Ul> <Li> Access to new data: Much historical data has been lost . Even archives have to make decisions based on space and interest on what original material to obtain or keep . At times documents are discovered or publicized that give new views of well established events . Archived material may be sealed by Governments for many years, either to hide political scandals, or to protect information vital for national security . When these archives are opened, they can alter the historical perspective on an event . For example, with the release of the ULTRA archives in the 1970s under the British 30 years rule, a lot of the Allied high command tactical decision making process was re-evaluated, particularly the Battle of the Atlantic . The release of the ULTRA archives also forced a re-evaluation of the history of the electronic computer . <Ul> <Li> New sources in other languages: As more sources in other languages become available historians may review their theories in light of the new sources . The revision of the meaning of the Dark Ages are an example of this . </Li> </Ul> </Li> <Ul> <Li> New sources in other languages: As more sources in other languages become available historians may review their theories in light of the new sources . The revision of the meaning of the Dark Ages are an example of this . </Li> </Ul>

Orthodox view of a historical event or period