Identify the extended simile in this passage. how does it add meaning to the text?

"sudden as hungry wolves the kids purloin
or lambs, which haply some unheeding swain
hath left to roam at large the mountains wild;
they, seeing, snatch them from beside the dams,
and rend incontinent the feeble prey,
so swift the danaï the host assail'd
of ilium; they, into tumultuous flight
together driven, all hope, all courage lost."