John Chadwick assisted Michael Ventris in the decipherment of Linear B, and has been deeply involved with the reading and interpretation of both the survivng Linear B tablets and the Mycenean archeological record. In his book "The Mycenean World (Cambridge University Press, 1976) he has a chapter entitled "Homer, the pseudo-historian". This note draws heavily, but not exclusively, on Chadwick's chapter.
Until Scliemann discovered Troy in the mound of Hisalik, Homer's tales had been taken to be a rousing good story, in the same way as Shakespear's plays are just stories, even when they are labelled "Histories". After Schliemann, the pengulum swung the other way, and to some extent everything told by Homer was taken to be at least possibly true, and the tales of the Iliad and the Odyssey to be a guide to Aegean history. Neither position is necessarily reasonable.
Where do we get our information about what actually happened in past times? If somebody wrote an eyewitness report in a language we can understand, we can expect that there is some relation between what was written and what actually happened, even though most reports of significant events are strongly biased by the leanings of the teller, whether victor or vanquished. If several people wrote about it from different viewpoints, and the accounts more or less agree, then we can be reasonably sure that things happned the way the writings say at the points of agreement. But when there is no written record, we have to use forensic methods, like a detective investigating a murder.
What is the evidence in the case of Homer's writings about the Trojan War and its aftermath? There is what remains of Troy, a settlement occupied over several thousand years, sometimes as a poor town, sometimes as a magnificent one. There is what remains of Mycenean cities and settlements both in Greece (including Crete) and in what is now Turkey. And there are clay tablets preserved by the accident of having been in buildings that burned, baking them for posterity.
In Mycenean practice, it seems that clay tablets were not used for material intended to be preserved, but for records of a single year's administration. Probably, the permanent records were kept on papyrus or something similar; the shapes of the characters do not suggest that clay was their primary habitat, though as a temporary recording surface it was quite probably cheaper than imported papyrus. It is an accident of history that allows us to see what the writers never intended to last for more than a year or so, while being unable to see what they intended to last.
A thousand years earlier, in contrast, the cuneiform tablets in Ebla appear to be archival records of state transactions, as well as of diplomatic and espionage messages. For example, the treaty between Ebla and Ashur (later the capital of the Assyrian Empire) is inscribed on clay. Several decades worth of records from around 2500 BC were in the archival library of 15,000 tablets found early in the Ebla excavations. They record economic, political and military dealings with the neighbouring region, from the Black Sea to the Mediterranean to the Persian Gulf.
Cuneiform writing is much more suited to clay than are Linear A or Linear B, which suggests that clay was the primary writing surface for the earlier records, as it was not for the later Cretan and Mycenean.. We do not have textual documentation from Troy itself, though there are some Hittite records that might relate to what we know as "the Trojan War." These, however, are hard to interpret in the context of the Iliad.
In the absence of textual records, the archeological record tells much, but not all. It can tell, for example, that there once was a great city with dominating walls on the site at Hisalik, and that the geographic configuration is as Homer describes. It can tell that the city with these walls was succeeded by a cramped, impoverished town. It can tell that the great walls were probably broken by a major earthquake (Troy is on a fault line along which earthquakes tend to progress westward. Troy is at the western entrance to the Sea of Marmora--in very recent times, only a few months before our holiday tour, a devastating earthquake caused considerable loss of life around Izmit, not far away, at the eastern end of the Sea of Marmora.).
What archaeology cannot tell is the names of the participants, the length of a siege, or the ebb and flow of battle. What it can sometimes say is whether there is a cultural change that can be ascribed to an occupying force, or--as in the case of Troy, that a rich, monumental city was destroyed and replaced by a poor one whose houses filled the spaces that had been palaces. Something did happen in Troy.
If some of what Homer wrote is accurate, where did he get it from? In Homer's time, in Greece, the idea of writing was known--obviously, since Homer wrote--but very few people could write. Homer describes a written message as being somehow magical, and the sender of the message did not expect the courier to be able to read it. Homer was writing in what is known as the "Greek Dark Ages" that followed the destruction of the Mycenean cities and the rise of the classical Greek cities perhaps 600 years later.
In those Dark Ages, as in the European Dark Ages of similar duration following the collapse of the Roman Empire, historical tradition had to be carried orally. It is from the tales of bardic singers, singing stories of conquering heroes, that Homer wove his tale. But Chadwick asserts that Homer's language, known to us only through a 300-year later transcription, is not the language of bards. It is the language of a poetic writer, in which traces of the bardic singer's language can be found. Homer, or the later transcriber, fit the songs into a new format, and quite probably mixed and matched songs to make a coherent story.
Why should we think that anything Homer wrote was historically accurate? It is mainly because he wrote about things of which he could not have had first-hand knowledge, but of which we have archaeological knowledge. Why should we think that the story is not totally accurate? Because we know at least of anachronisms, of things described that did exist as he described, but not at the time of which he writes. For example, the Mycenean helmet made of boars' tusks did not exist in Homer's time, and had been forgotten by the putative time of the Trojan War, but it did exist at the time the Myceneans administered Crete after the explosion of Thera, two to four hundred years before the probable date of the Trojan War (the dating of this era is very confused). Chadwick says: "There are more than a few indications that elements in the Homeric poems go back not to the end of the Mycenean period, but to an earlier phase. One character in the Iliad has the great body shield described as 'like a tower', yet these seem to have gone out of use a couple of centuries earlier."
There are things that should have been mentioned, had the Iliad been a proper historical record, but were not. Homer describes cremation as the way of disposing of the dead, but never mentions the great Tholos tombs that were a prominent feature of the Mycenean world. Homer does not use the distinctions among the leadership that are clear in the Linear B tablets, and that must have been clear to the Greek participants in the Trojan War. Homer's list of the cities involved in the war omits most of the major Mycenean cities--they had been destroyed and the population dispersed very shortly after the date ordinarily assigned to the War. He does mention Mycenae and Tyrins, whose walls are even now quite impressive, although he locates Mycenae in the wrong place, further north, along the shore of the Gulf of Corinth.
Across the gulf of the European Dark Ages, there is a similar story recording an actual event in songs that were written as a single poem five hundred years later. Here is a quote from Chadwick:
"We have... the parallel of the mediaeval Song of Roland which, apparently composed in the twelfth century, relates an event that occurred in the year 778. ... Oral tradition could perfectly well preserve historical facts for many centuries, but... it has a habit of distorting the truth and introducing serious errors into the account. The Song of Roland even has the wrong enemy; and other epics introduce into the story characters who were not contemporaries."
The Morte d'Artur may also be a fanciful reconstruction from tales and songs about a real warrior hero at the end of the Roman Empire--certainly the name of King Arthur was well known centuries before Mallory. But do we take Mallory as writing anything more than a magical mystery story in which he imposes his medieval ideas about ancient life upon the bare bones of a possibly true tale? There is no reason to believe that the Iliad is any more--or any less--reliable as a witness to history.
A discussion of the Trojan War is here.