Although by the time the story gelled to a written tale, it came to reflect the political realities of contemporary Greece.

We think the war was fought sometime around 1300 BC, from archaeological evidence (I'm doing this from memory, so feel free to look it up and check the details), and probably represents a power struggle between a coalition of Mycenaen kingdoms with a Persian vassal state. We have no idea what the fight was about, but my guess is it was about trade. The story gelled into its present written form around 800-900 BC, during which time the Athenian and Spartan city-states arose and the Mycenaen empire collapsed, and even the ethnicity and language of the participants had changed.

A lot happened in between. The war was fought between Bronze Age pre-literate cultures (neither iron weapons nor writing are mentioned anywhere in Homer), and when the story finally stabilized into its present written form it was already very old, a relic of the ancient times before the Greek Dark Ages when barbarian invaders from the North moved in and filled the vacuum left by the vanished Mycenaens.

The war may have either been a single battle, or a campaign that lasted on and off for centuries. We simply don't know for sure.

There are a lot of clues, but few hard facts in the narrative; but a few items give tantalizing glimpses into the dim past. For example, the Classical Greeks were a very misogynistic society, but Homer is full of wise, strong, independent women, both mortals and goddesses. Also consider how the kingship of Ithaka is determined by who marries Penelope--political power is transmitted by the female line, not the male issue. Its a matrilocal and matrilineal culture, Telemachus does not automatically become king just because Odysseus is supposedly dead.

To the ancient Greeks, the Iliad and Odyssey must have been like the legend of King Arthur is to us, an idealized look at a mythical past. Arthur would have been king of the Britons about 500 AD, but Geoffrey of Monmouth first writes about him 700 years later, and even his contemporaries thought Geoffrey was a liar and a fraud. The story finally stabilized into roughly its present form in the 1500s.