An interesting citation from the 'battle of the gods' is Il 20.67
Always in Homer's version of the Troy story, Apollo and Poseidon find themselves on opposite sides. Scholars have wondered why this is the case. See e.g. Il 24.25-
Poseidon and Zeus are also in a somewhat ambivalent relation. Perhaps because Zeus was born the youngest of three brothers but (like his father Kronos) he became the leader of the gods (Il 13.355). Normally of course it is the eldest son who takes the inheritance. So, like Jacob in the bible, Zeus 'becomes first-born'(1). Poseidon accepts this but not wholeheartedly and there is clearly some tension left. See most clearly Il 15.157-219. There are a number of other features which are important:
All this forms the context in which Homer's picture of Poseidon is drawn. I find it likely that members of this family, as I suppose Homer was, would refer to their city as 'Pylos-on-the-beach' and that when they refer to the will of Poseidon, they refer to a long-standing family policy aimed at acquiring a strong power-base on the Asian mainland. In terms of the Homeric picture: Poseidon, like the Ionians, 'has the sea' but 'wants the land'. Zeus (or Fate) however says that he cannot have it. See Il 15.187-. The whole picture suggests strongly that Poseidon has Kronos-like ambitions: he wants to rule (again?(2)) on earth.
The myth of the Ionian migration as an early mass movement from or through Athens, led by Neleus and Medon, is not accepted as a literal historical fact anymore. I would like to propose an alternative: not a mass movement but a slow trickle of emigrants, organised by and provided with leadership by a branch of the Neleids operating from Athens. It must have been a long term policy possibly inspired by the 'Dorian invasion' which may have been a similar slow penetration movement inspired by a charter myth. If this is true, the Ionian movement must have been late rather than early in the dark age.
Let us translate the myth: to become king again (-> Hera) the Neleids (-> Poseidon) have devised a clever plan of war (-> Athena) to conquer themselves a power base in Asia (-> "Troy" but actually the two great floodplains of western Anatolia). As political banner they use the charter myth of the story of the abduction of Helen. This emigration policy seems good for everyone, but it cuts two ways: it lessens the population pressure and risk of stasis on the mainland, but, if successful, it is also likely to make the organizing Neleid family far more powerful than any single power in mainland Greece. That would contravene the oath of the Styx and endanger the rule of Zeus.
Homer presents this rivalry between these gods in a fairly light-hearted way, but I think there may be a dangerous tension in the Greek world behind it:
Curiously, in this scene Zeus is portrayed as obeying Hera (οὐδ' ἀπίθησε πατὴρ ἀνδρῶν τε θεῶν τε, Il 4.68). see also: Il 8.198-212 (Hera wanting Poseidon to act but he is unwilling to face Zeus), Il 15.178- (Zeus threatening to fight him).
There is also a link with the 'golden rope' episode in Il 8.19:
But there may be another layer to the Poseidon picture. Homer, as I argue elsewhere, was a member of the Neleid family. Family is everything in those days, it transcends the individual, especially for aristocrats. So Poseidon, the claims of his family, would have been a major part of his upbringing, his life. So he would feel the claims of Poseidon but had come to the conclusion that the demands of Zeus superseded those. An internal conflict like this would explain much of the complicated role that Poseidon plays in the Iliad (and the Odyssey). Giving in, unwillingly, to Zeus, wanting Troy to fall but saving Aeneas, his curious relationship with Apollo, his hatred of Odysseus.