The armies massing…crowding thick-and-fast
as the swarms of flies seething over the shepherds’ stalls
in the first spring days when the buckets flood with milk –
so many long-haired Achaeans swarmed across the plain
to confront the Trojans, fired to smash their lines.
The armies grouping now – as seasoned goatherds
split their wide-ranging flocks into packs with ease
when herds have mixed together down the pasture:
so the captains formed their tight platoons,
detaching right and left, moving up for action.
The Iliad, Book 2, lines 555-564. The terrifying sight of thousands of Achaean troops gathering to prepare for war is described here in an epic simile, likening them to clouds of angry flies swarming over the plain to confront and smash the Trojan enemy. What the Duke of Wellington said about his own troops comes to mind: "I don’t know what effect these men will have upon the enemy, but, by God, they frighten me."