The Iliad, Book 2

Zeus sends a Dream in the form of Nestor to convince Agamemnon to lead a (doomed) assault against the Trojans.  To convince them, Agamemnon instead tells the Greeks that Zeus has convinced him the best course is to turn back, shaming them in the process.  The plan backfires (?).  They begin the retreat, but Hera sends Athene to appear to Odysseus, convincing him to convince the Greeks that honor requires they stay and fight.  Thersites says that's nuts.  Odysseus beats the crap out of him.  Thus convinced, the forces are marshalled and sacrifices performed.  A census of the Greeks.