Then both went thrashing into the lines to make a slaughter
as two wild boars bristling, ramping back for the kill,
fling themselves on the yelping packs that hunt them –
back they whirled on attack and laid the Trojans low
while Achaeans just in flight from Hector’s onset
leapt at the chance to gather second wind.

– Homer

The Iliad, Book 11, lines 375-380. As the Greek army begins to retreat, Odysseus and Diomedes decide to make a stand. They heroically fling themselves at the Trojans like "two wild boars" going in for the kill, as described in an epic simile. Their action inspires the other Achaeans.