In the Iliad, the gods interfere in the war all the time, and Zeus holds the plan. In Book I, he nods to Thetis that he will honor Achilles, which costs the lives of many Greeks: "and the design of Zeus was fulfilled." In Book II, he sends a Dream to deceive Agamemnon. In Book VIII, he forbids the other gods to help either side: whoever disobeys "will return to Olympus struck," and he declares that none of them could drag him from the sky to the plain.
The other gods take sides. Hera and Athena support the Greeks, and Athena holds Achilles by the hair in Book I, deceives Hector with the figure of Deiphobus in Book XXII, and gives strength to Diomedes in Book V. Apollo and Aphrodite support the Trojans: Aphrodite saves Paris, Apollo disarms Patroclus and abandons Hector when the scale goes down. In Book XIV, Hera seduces Zeus with the belt of Aphrodite and puts him to sleep so that Poseidon can help the Greeks.
The gods also have limits. In Book XVI, Zeus considers taking his son Sarpedon out of the fight, and Hera answers: "a mortal man, long ago destined by fate, do you wish to free him again from death?" and he yields. An almost identical line appears in Book XXII, spoken by Athena, when Zeus hesitates to save Hector. The gods can change the day-to-day course of the battle, but they do not seem able to change a fate already fixed.
The contrast with men is marked. The gods quarrel and laugh: in Book I, "inextinguishable laughter" rises among them as they watch Hephaestus bustling about the hall, while on earth many die. For some readers, this is what gives weight to human death; for others, it shows that the source of destiny lies outside men, and that all that is left to them is the manner of facing it.