Greeks

The Greeks believed that the earth was formed before any of the gods appeared. The gods, as the Greeks knew them, all originated with Father Heaven, and Mother Earth. Father Heaven was known as Uranus, and Mother Earth, as Gaea.

Uranus and Gaea raised many children. Among them were the Cyclopes, the Titans, and the Hecatoncheires, or the Hundred- Handed Ones. Uranus let the Titans roam free, but he imprisoned the Cyclopes and the Hundred- handed Ones beneath the earth. Finally, Gaea could not bear Uranus's unkindness to the Cyclopes and the Hundred-Handed Ones any longer.

Gaea joined Cronos, one of the Titans; and together, they overcame Uranus, killed him, and threw his body into the sea. Aphrodite, goddess of love and beauty, later rose from the sea where Uranus's body had been thrown. Now Cronus became king of the universe. Cronos married his sister, Rhea, and they had six children. At the time of Cronos's marriage to Rhea, Gaea prophesied that one of his children would overthrow Cronos, as he had overthrown Uranus. To protect himself, Cronos swallowed each of his first five children -- Hestia, Demeter, Hera, Hades, and Poseidon -- immediately after birth.

After the birth of her sixth and last child, Rhea tricked Cronos into swallowing a rock and then hid the child -- Zeus -- on earth. Zeus grew up on earth and was brought back to Mount Olympus as a cupbearer to his unsuspecting father. Rhea and Zeus connived against Cronos by mixing a noxious drink for him. Thinking it was wine, Cronos drank the mixture and promptly regulated his five other children, fully grown. Then Zeus and his brothers waged a mighty battle against Cronos and the other Titans.

Cronos and the Titans were defeated when Zeus ambushed them with the help of the Cyclopes and the Hundred-Headed Ones, and they panicked and retreated. Cronos and the Titans were imprisoned in the Earth where their fighting still causes earthquakes from time to time. Zeus and his brothers and sisters went to live on Mount Olympus, where they ruled over the earth.With our view of God, it can sometimes be difficult to comprehend the actions and thinking of the Greek deities. The Christian God does not tend to take such an active role in the affairs of people's lives, where, on the other hand, the Greeks regarded direct involvement by the gods as a daily, uncontrollable part of life.

Needless to say, divine intervention was a major variable in the equation of Homer's Iliad.
The gods picked who they would favour for different reasons. Except Zeus: As the symbol of supreme authority and justice, he makes judgement calls as to the other gods' involvement in the war, remains impartial, and doesn't seem to get caught up in picking favourites. Even when his own son, Sarpedon, was about to die, Zeus chose to let the outcome go unaltered.

On the other hand, Zeus's wife, Hera, displayed the more typical actions of a god. After Paris, a Trojan, judged Aphrodite the fairest over Hera, and, after her daughter Hebe was replaced as cupbearer to the gods by a young Trojan boy, she was quite resentful towards Troy and its people. Obviously she sided with the Greeks and would stop at no length to express her will. Scheming and manipulating she even dared to trick her husband, King of the Gods.

Hera, along with Athena, who was also passed over by Paris, is seen as the chief divine aid to the Greeks.
Being the god of the sea, Poseidon was another strong supporter of the ocean-faring Greeks. Whenever Zeus turned his back Poseidon tried to help the Greeks in the fight. Poseidon felt that he was somewhat Zeus's equal as his brother, but recognizing Zeus's authority and experience, he looked to Zeus as an elder.
There were also Gods who favoured the Trojan side of the conflict.

Both Apollo and Artemis, twin brother and sister, gave aid to the city of Troy. Although Artemis takes a rather minor role, Apollo, perhaps angered by Agamemmnon's refusal to ransom Khryseis, the daughter of one of his priests and was constantly changing the course of the war in favour of the Trojans. Responsible for sending plague to the Greeks, Apollo was the first god to make an appearance in the Iliad. Also, mainly because Apollo and Artemis were on the Trojan side, their mother, Leto, also helped the Trojans.
Aphrodite, obviously supporting Paris's judgement, sided with the Trojans.

Although she was insignificant on the battlefield, Aphrodite was successful in convincing Ares, her lover and the god of war, to help the Trojans.
One view of the gods' seemingly constant intervention in the war was that they were just setting fate back on the right course. For instance, when Patroklos was killed outside of Troy, Apollo felt no guilt for his doings. It had already been decided that Patroklos would not take Troy, he should never have disobeyed Achilles in the first place.

As a god, he was just setting fate on a straight line. Achilles laid blame on Hektor and the Trojans. He did not even consider accusing Apollo, who never came into question, although he was primarily responsible for the kill. Apollo's part in the matter was merely accepted as a natural disaster or illness would be today.
This general acceptance of a god's will is a recurring trend throughout the poem. A prime example of this trend is in book XXIV.

Achilles, angry over the death of Patroklos brutally disgraced Hektor's body. Tethering Hektor's corpse through the ankles, Achilles dragged him around Patroklos's tomb every day for twelve days.
This barbaric treatment was uncalled for and displeased the gods greatly. Achilles mother, Thetis, was sent by Zeus to tell him to ransom the body back to the Trojans.

One may think Achilles would be possessive of the body and attempt to put up a fuss as he did before with Agamemmnon in Book I. But, Achilles showed humility and respect for the gods and immediately agreed to ransom the body to the Trojans, showing that all mortals, even god-like Achilles, were answerable to the gods.
This ideology would seem to give the gods a sort of unlimited freedom on earth, although, the gods could not always do as they pleased and eventually had to come before Zeus. Zeus acted as a balance of sorts throughout the Iliad. He had to keep the gods in order and make sure that what fate decreed would happen.

For example, after Achilles re-enters the battle Zeus declared that if Achilles was allowed to go on slaughtering the Trojans with nothing to slow him down, he would take Troy before fate said it would happen. Therefore, to counter Achilles massive retaliation against the Trojans, Zeus allowed the gods to go back to the battle field.
In Zeus's own interests, he preferred to deal with issues more personal to the individual heros of the Iliad. This can be seen throughout the book as Zeus attempted to increase the honour of certain individuals.

Zeus knew that Hektor was going to be killed by Achilles, and, feeling sorry for Hektor Zeus attempted to allow Hektor to die an honourable death. For instance, when Hektor stripped Achilles armour off Patroklos, Zeus helped Hektor "fill out" the armour so he would not seem like less of a man then Achilles. Zeus also gave his word to Thetis that Achilles would gain much glory showing his involvement on a personal level.
Homer used the gods and their actions to establish twists on the plot of the war. It would not have been possible for him to write the story without the divine interventions of the gods. Indeed, they affected every aspect the poem in some way, shape or form.

Yet, from the immortal perspective of the Greek god, the Trojan war, and everything related to it, was only a passing adventure in the great expanse of time.