The story of Helen and the Trojan War was a Charter Myth
for the Ionian migration in the same way the story of
Heracles' children claiming their inheritance was a charter
for the Dorian invasion. These stories functioned as political banners
and were actively promoted by leaders of those movements,
in this case: a channeling of migration to
Ionia, through Athens.
It is easy to see why: travel through today's western Turkey and you will see
that the floodplains of the rivers 'Gediz' and 'Büyük Menderes', then called the Hermus
and the Meander, are prize land, larger and more fertile than any land in
mainland Greece. A nice powerbase for any clan with royal aspirations.
If this is true, it is easy to see that the
Iliad is a very political poem and that the poet would need a 'hidden'
level of meaning to discuss these topics. Ionia in Homers day was a
society under threat of war and Homer was writing about this war.
Although he created an epic distance by, for instance, not mentioning
Ionia and by stressing the fact that these stories took place a long
time ago ("conscious archaization"), he still would have made a lot of
enemies by his anti-war stance. He effectively says: "Zeus will give us
Troy one day, but not now".
I place Homer in Smyrna, and Smyrna's Troy was Sardis, the main stronghold of the not-yet-unified Lydians. These were the people that Smyrna built its imposing wall against though that did not stop the Lydians sacking their city by the end of the 7th century.
The Iliad, while set in Homer's past, is about a crisis of his present day: the failure of the Ionian migration. "νῦν ἄμμε παλιμπλαγχθέντας : now that we have been rebuffed" (Il 1.59). This was a movement, organized/stimulated by a powerful family in Athens called the Neleids, rulers in Pylos in the past and probably a "great house" dating back to Mycenean times, even claiming descendance from Poseidon. They found a new powerbase in Athens but they had branches everywhere. In the Iliad they are represented by Nestor and Poseidon).
The aim of their policy was to increase the stability of the mainland by emigration (of landless younger sons of nobles and other 'superfluous' men) and with these people build an army in Ionia, aiming to conquer the two great floodplains of the Hermus and the Maeander. The important Greek cities in this plan, in Homer's time, were Smyrna and Miletus.
A glance at the map will show how little they succeeded. After a number of generations of this Ionian migration they still found themselves on a small strip of land on the coast, 'leaning against the shore', as Homer calls it, unable to defeat the inhabitants of the plains who were both numerous and skilled in fighting. This caused a crisis for, while immigration went on, the available land did not grow. So the Neleids' plan had to be put on hold, emigration redirected to other lands. Miletus, for instance, even became the mother city to a large number of settlements elsewhere.
The focus of Homer's story seems to be on Smyrna, situated near the Hermus delta, separated from the plain by mountains. The Hermus plain, later to become Lydia the richest country of the time, was not yet unified but it was led to a degree from a high, impregnable stronghold called Sardis.
As the poet Mimnermus of Colophon (his name means 'remember the Hermus') testifies, troops from Colophon and Smyrna fought many a battle in this plain, without success.
Sardis is Smyrna's Troy. Homer carefully avoids all mention of Smyrna and Sardis or any open reference to the contemporary situation. We may suppose that the whole cycle of stories about Menelaos and Helen and the thousand ships that sailed to get her back, functioned like a charter-myth for the migrants to justify their conquering 'Troy'. Living in a city at war, it is a dangerous thing to say "you can't win this" and that is exactly what Homer is doing, as well as criticizing the in-revenge-for-Helen concept. The situation in Smyrna in his day must have been very feverish and tense. While they went on the attack sometimes, the very presence of their enormous city wall also shows that they were under real threat. The story of the second city on the shield (Il 18.509-40) may be a glimpse of the situation. The climax of the Iliad is the freeing of the beleaguered Achaean 'city' (it's a shipcamp with a wall) by Achilles, the 'Hero of the counter-attack'. Its conclusion is: defend your city with all your might, but do not go to the gates of Troy for it will be your death.
A song with controversial subject like the Iliad could not have been sung without the backing of powerful patrons. The Neleids would certainly have been outraged by it. (This also ties in with the tradition of Homer's exile from Smyrna, which was ruled by a member of the Neleid family.) My guess is that there was a strong movement for the pacification of Greece and the end of stasis. Linked to this are the foundation of Delphi, the formation of regional leagues, the establishment of the Olympic games and the creation of a more or less unified olympic religion made known by cycles of stories of heroes from all over Greece and hymns to the gods defining their sphere of power (such as Hesiod), and a definition of the polis. This pacification of Greece also included Ionia.
The attempt to freeze the political situation for instance, is nicely reflected in the story of Helen: Menelaos (Sparta) had been acknowledged victor (the most powerful one), possibly after the first Messenian war. Symbol of this is Helen, the Prize(1). Everyone agreed to come to Menelaos' aid if anyone attempted to steal Helen (victory) from him.