These horses on the Francois vase are doubtless not the celebrated Balius and Xanthus, those proud horses given to Peleus at his wedding by the Earthshaker, Poseidon. But they recall them, in some fashion.
This time we will save you, mighty Achilles,Immortal horses. Its a great idea, and the fact that one of them talks makes them even more compelling. In this scene (from the poem, not the vase) Achilles has scolded the horses:
This time--but your hour is near. We
Are not to blame, but a great god and strong Fate. (Iliad, 20, Lombardo)
Xanthus and Balius, Podarge's famous colts,
See that you bring your charioteer back
Safe this time when we have had enough of war
And not leave him for dead, as you left Patroclus. (Iliad, 20, Lombardo)
I have to think Achilles is being grimly ironic here, teasing his horses as he might any companions as they head out to battle. Their sudden response (actually, only Xanthus can speak) has a very different tone, which I think must always be the case when immortal horses speak to us. Achilles is not happy with their answer. I think it is a great exchange in showing the gulf between Achilles and these immortal beasts. And I think Kleitias knew from horses.