It's interesting reading through a progression of Greek writers. In the past year we've read through Homer's telling of the Trojan war, Herodotus and the Persians and coming up, Thucydides and the Peloponnesian war. There is a rather big change from Homer to Herodotus and then the big T.
Homer's telling of war was completely driven by the gods. They planned the war, they picked out who would die and often helped them on their way. The gods even fought over how to kill off the survivors. In Homer's world, the gods stood in for fate and decided who would make it out alive.
Herodotus is much less into the divine. His stories are driven by great people and the decisions they make. He does emphasize messages from oracles. They're conduits of the gods but we no longer have any insight into the motives behind fated actions.
Thucydides writes about war in an almost modern fashion. Decisions are made solely by people and battles are won or lost based on who was best prepared and best led. He mentions phrases from oracles only in the way that they might have matched events. He also mentions temples and shrines but only to show the respect that people paid to them. His is a history in which other people have custom and possibly belief, but you couldn't prove that he has either.