I made a comment, in a comment, a bit ago that history is only ever partial. This is in fact ambiguous, and, possibly, was so deliberately. History is partial, in that we can only ever deliver a part of history in our historical writing (or any other medium, for that matter) and history itself, as written, is biased, inevitably. In fact, things are a little worse than that.
We all have a history. We stand, as Newton observed, on the shoulders of giants, or at least we live within a given culture and society which has shaped us. The culture and society itself is shaped by its history. Thus, our worldviews, standpoints and biases are shaped by those of our society and its history. There is no getting away from this. We all have to stand somewhere, and the somewhere that we stand is going to have blind spots.
To use a way of thinking about this that I have used before, we all have a horizon. Stuff within the horizon is interesting to us, stuff outside it we neither know nor care about. If we stumble across something that is outside our horizon, then usually we will ignore it as not being interesting or relevant. Of course, our horizons are not static. Things can move from outside to within as we develop new interests. Similarly things can move from within the horizon to outside, as we lose interest.
Gadamer has the view that as we learn something our horizon fuses with the other. Thus, if we read an ancient historian, we have, to understand him, fuse our horizon with his. Notice that we do not replace one horizon with another. The fusion carries over from our previous one; it is, so to speak, merely expanded, in terms of trying to understand, say, Tacitus. We bring to our reading of Tacitus the interests and understandings that we had before. If we are attentive, intelligent, rational and reasonable in our reading, we will hopefully emerge from it with a broadened horizon, one which incorporates insights from Tacitus into our worldview.
In terms of history, of course, this sort of thing starts to impinge on the nature of history itself. As it turns out, history (like so many things) is difficult to define precisely. It is one of those things that we know when we see it. But the horizon of the historian and the horizon of the times contribute to the sort of history we write and want to read. The questions which an investigator has will be different, according to both the investigator’s own interests and those of the times in which they live.
For example, there is much interest in classical history into Greek and Roman homosexuality. There are more papers and monographs in the last thirty years or so than you could shake a stick at. But if you probe further back into historiography, you tend to find less and less interest in the subject. The reasonable conclusion to be drawn from that is that historians were simply not interested in the subject. For the most part it was illegal, of course, but it was also something that most consumers of history were simply not interested it. Therefore, not much work was done on the subject, and that which was, was mostly ignored, or tried to explain away the activity as it is presented in our sources. In recent culture, of course, there has been much discussion of gay partnerships, marriages and so on, and so we should not really be surprised by historians asking questions about homosexuality of their sources.
History as it is investigated, then, is mediated by the society in which the historian is situated. However, as I mentioned above, history is always partial. A historian cannot give a full account of the past. Firstly, of course, sources to do so are not available. But even if such sources were there, a historian would have to select from them. Sources do not, as it were, speak. The historian must interpret them and speak for them. So they much choose from the range of sources before them which to present, and how they are going to do so coherently. The selection, of course, will be with respect to their own interests and those of their society. This partiality is nothing to do with any prejudices the historian or their society have; it is simply a matter of being able to do anything by selecting those sources which seem most important.
This has a number of results. As society shifts and moves, history has to be re-written. A few decades ago it was popular to see, for example, the English Civil War through a Marxist lens and hence to observe class war, or the rise of the gentry (or the fall of the gentry – history is never neat and tidy), to view the Levellers and Diggers as proto-communists and so on. Now things have changed (except, I suppose, on the hard Left) and the Diggers and Levellers are viewed radical splinter groups of no great significance, and most of the blame for the war is placed on Charles I. History, therefore, has to be re-written to account for this, which is, at least in part, due to the collapse of the Soviet Bloc as a viable economic alternative to rampant capitalism.
Similarly, as wargamers, we read history partially. I am sure I am not the only wargamer to have skipped over the boring bits of history to track down the battles and armies, the nature of tactics and the experience of battle. These are, of course, valid bits of history, but we do need to recall that they are only bits of history. History itself is much bigger and more complex than just the wars and battles. Eventually, even as wargamers, we should emerge from this and start wondering about how the people lived, about what their world view was. As such, history turns into something much deeper and richer than a list of battles, disasters and diseases, and we, hopefully, become more rounded human beings as a result.