Platte, Ryan. 2017. Equine Poetics. Hellenic Studies Series 74. Washington, DC: Center for Hellenic Studies. http://nrs.harvard.edu/urn-3:hul.ebook:CHS_PlatteR.Equine_Poetics.2017.
2. Horses, Heroes, and Sacrifice
Heroes as Horses and Horses as Heroes
This horse is also mentioned in the Iliad in connection with other divine horses:
οὐδ’ εἴ κεν μετόπισθεν Ἀρίονα δῖον ἐλαύνοι
Ἀδρήστου ταχὺν ἵππον, ὃς ἐκ θεόφιν γένος ἦεν,
ἢ τοὺς Λαομέδοντος, οἳ ἐνθάδε γ’ ἔτραφεν ἐσθλοί.
The local Trojan horses mentioned here are the divine horses given to Laomedon by Zeus as recompense for the abduction of Ganymede. The horses of Aeneas, which feature so prominently in the Iliad due to their abduction by Diomedes and subsequent victory in the chariot race at the funeral games of Patroclus, are descendants of these horses.  In book XX, Aeneas recalls the story of the three thousand mares of Erichthonius, which mated with Boreas, the god of the North Wind, and produced twelve colts that could run over the top of the sea. 
θήλειαι, πώλοισιν ἀγαλλόμεναι ἀταλῇσι.
τάων καὶ Βορέης ἠράσσατο βοσκομενάων,
ἵππῳ δ’ εἰσάμενος παρελέξατο κυανοχαίτῃ·
αἳ δ’ ὑποκυσάμεναι ἔτεκον δυοκαίδεκα πώλους.
αἳ δ’ ὅτε μὲν σκιρτῷεν ἐπὶ ζείδωρον ἄρουραν,
ἄκρον ἐπ’ ἀνθερίκων καρπὸν θέον οὐδὲ κατέκλων·
ἀλλ’ ὅτε δὴ σκιρτῷεν ἐπ’ εὐρέα νῶτα θαλάσσης,
ἄκρον ἐπὶ ῥηγμῖνος ἁλὸς πολιοῖο θέεσκον.
νῦν μοι τὴν κομιδὴν ἀποτίνετον, ἣν μάλα πολλὴν
Ἀνδρομάχη θυγάτηρ μεγαλήτορος Ἠετίωνος
ὑμῖν πὰρ προτέροισι μελίφρονα πυρὸν ἔθηκεν
οἶνόν τ’ ἐγκεράσασα πιεῖν, ὅτε θυμὸς ἀνώγοι,
ἢ ἐμοί, ὅς πέρ οἱ θαλερὸς πόσις εὔχομαι εἶναι.
The fact that these horses drink wine at all distinguishes them from other animals since wine is a mark of human civilization. This act essentially isolates a species boundary, a boundary that positions horses as closer to humans than to other animals. The use of the phrase ὅτε θυμὸς ἀνώγοι is also striking and is translated here as “whenever your heart bade,” and is assumed to refer to the horses. It could, however, be argued that this clause refers to Andromache’s desire rather than to the horses’, that it should be translated as “whenever her heart bade.” Yet the formula πιέειν ὅτε θυμὸς ἀνώγοι appears elsewhere twice in the Homeric corpus and in each case πιέειν complements ἀνώγοι,  so the heart of the figure by whom the wine is to be drunk is the subject of the verb ἀνώγοι. If that relationship holds true in this usage then the horses here display a degree of agency otherwise reserved for humans. It may be pointed out that this entire line was athetized by the Alexandrian editors, signaling their discomfort with the depiction of the horses drinking wine at all. Be that as it may, the image did appear in the ancient tradition, and did so because the offering of wine to heroes was a regular feature of Greek oral song and these horses are here treated as heroes, rather than as ordinary animals.
τίς τ’ ἂρ τῶν ὄχ’ ἄριστος ἔην σύ μοι ἔννεπε Μοῦσα
αὐτῶν ἠδ’ ἵππων, οἳ ἅμ’ Ἀτρεί̈δῃσιν ἕποντο.
Her inspired answer is:
τὰς Εὔμηλος ἔλαυνε ποδώκεας ὄρνιθας ὣς
ἀνδρῶν αὖ μέγ’ ἄριστος ἔην Τελαμώνιος Αἴας
ὄφρ Ἀχιλεὺς μήνιεν· ὃ γὰρ πολὺ φέρτατος ἦεν,
ἵπποι θ᾽, οἳ φορέεσκον ἀμύμονα Πηλεί̈ωνα.
ἀσπίδι γιγνώσκων αὐλώπιδί τε τρυφαλείῃ,
ἵππους τ’ εἰσορόων.
It is ironic that these horses by which Diomedes is recognized are the very horses that he will forsake for the semi-divine Trojan horses that he steals from Aeneas. Yet, the story of Diomedes in the Iliad is largely the story of a lesser hero stepping temporarily into the role of Achilles, and, in a sense, his heroic ascent is paralleled by his equestrian ascent. Pandarus, on the other hand, is best known for his archery and is unique among the Trojan fighters in not having any horses at all. When Aeneas asks him to assume the role of his charioteer in book V he does so because Pandarus has just explained that he has no horses of his own because he left them all in his homeland.  He says in line 201 ἦ τ’ ἂν πολὺ κέρδιον ἦεν, “it would have been much better [if I had brought horses].” It is difficult to avoid thinking that the life that he leads at Troy, tricked into breaking the truce and finally killed, pierced through the tongue by Diomedes, is somehow presaged by his unusual dearth of horses, the warrior’s standard accoutrement and the very status marker in which Diomedes is excelling.
σὴ δὲ βίη λέλυται, χαλεπὸν δέ σε γῆρας ὀπάζει,
ἠπεδανὸς δέ νύ τοι θεράπων, βραδέες δέ τοι ἵπποι.
ἀλλ’ ἄγ’ ἐμῶν ὀχέων ἐπιβήσεο, ὄφρα ἴδηαι
οἷοι Τρώϊοι ἵπποι
Nestor’s old age is mirrored in the slowness of his horses while the superiority of Diomedes is reflected in the high quality of his, despite the fact that the horses have only recently been stolen from Aeneas. That the horses did not originally belong to Diomedes is not an issue: his present status as a fighter is perfectly matched by his current steeds, perhaps especially because he has proven his superiority over Aeneas by taking those horses. Diomedes’ superior stature means that the worthier horses are properly his regardless of their provenance.
Ξάνθον καὶ Βαλίον, τὼ ἅμα πνοιῇσι πετέσθην,
τούς ἔτεκε Ζεφύρῳ ἀνέμῳ Ἅρπυια Ποδάργη
βοσκομένη λειμῶνι παρὰ ῥόον Ὠκεανοῖο.
ἐν δὲ παρηορίῃσιν ἀμύμονα Πήδασον ἵει,
τόν ῥά ποτ’ Ἠετίωνος ἑλὼν πόλιν ἤγαγ’ Ἀχιλλεύς,
ὃς καὶ θνητὸς ἐὼν ἕπεθ’ ἵπποις ἀθανάτοισι.
The mixture of mortal and immortal components in his chariot team reflects the genealogy of Achilles himself, the son of a goddess, Thetis, and a human, Peleus.  We hear twice in the Iliad, once from Odysseus and once from Apollo, that no one but Achilles can drive his horses properly and that this is due to a similarity in their makeup. One of these instances occurs in book X, when Dolon confesses to Odysseus that he spied on the Trojan camp because Hector had promised him the horses of Achilles in return. Odysseus replies:
ἵππων Αἰακίδαο δαΐφρονος· οἳ δ’ ἀλεγεινοὶ
ἀνδράσι γε θνητοῖσι δαμήμεναι ἠδ’ ὀχέεσθαι
ἄλλῳ γ’ ἢ Ἀχιλῆϊ, τὸν ἀθανάτη τέκε μήτηρ.
The team is unmanageable to others because it is partly divine but can be mastered by Achilles, who is also partly divine, the son of the goddess Thetis. Yet it is singularly important that neither Achilles nor his chariot team is entirely divine, because the narratological focus is frequently not on the two immortal horses but on the mortal one, Pedasos, just as the narratological focus of the epic is on Achilles’ mortality despite his superhuman stature.
δεύτερον ὁρμηθείς, ὃ δὲ Πήδασον οὔτασεν ἵππον
ἔγχεϊ δεξιὸν ὦμον: ὃ δ’ ἔβραχε θυμὸν ἀί̈σθων,
κὰδ δ’ ἔπεσ’ ἐν κονίῃσι μακών, ἀπὸ δ’ ἔπτατο θυμός.
δὲ διαστήτην, κρίκε δὲ ζυγόν, ἡνία δέ σφι
σύγχυτ’, ἐπεὶ δὴ κεῖτο παρήορος ἐν κονίῃσι.
Pedasos’ purpose, narratologically, is to die. Soon thereafter the immortal horses see Patroclus die as well, and as Zeus observes them shedding tears, he says:
θνητῷ, ὑμεῖς δ’ ἐστὸν ἀγήρω τ’ ἀθανάτω τε;
ἦ ἵνα δυστήνοισι μετ’ ἀνδράσιν ἄλγε’ ἔχητον;
These horses are also closely linked to Achilles’ immortal mother, Thetis, because they were given to Peleus as a gift from the gods when Thetis was forced to marry him. The plight of these immortal horses next to a mortal companion and accompanied by mortal riders recalls the frequent lamentations of Thetis at having been forced to marry a mortal and to bear a mortal child whom she must see die. It is the plight of immortals who are close to morals. The unusual combination of mortal and immortal in Achilles’ chariot team reflects the uneasy identity of Achilles himself, more than human but ultimately not fully divine. Pedasos’ tragic demise foreshadows Achilles’ own impending death as well as that of Patroclus, and we see that the Iliad’s tendency towards comparison of heroes and horses finds its most consistent expression in Achilles, the figure that is both most horse-like and most heroic.
Indic Horses and Indic Heroes
pruṣitápsum āśúṃ carkṛtyam aryó nṛpátiṃ ná śūram ||
yáṃ sīm ánu praváteva drávantaṃ víśvaḥ pūrúr mádati hárṣamāṇaḥ |
…ghṛdhyantam medhayúṃ ná śūraṃ rathatúraṃ ||
The Horse Sacrifice
The ritual could in fact be much more elaborate than this, and could involve as much as a full year of preparations, yet this summary will suffice for our current purposes. 
Regardless of any ethnic bias on the part of Giraldus, the details of this ritual seem too specific to be disregarded, and probably do reflect, at least in basic details, an actual ritual that is cognate with the aśvamedha. 
Human Sacrifice and the Equus October
He also discusses it under his entry for panibus:
I do not claim that this reflects a shared methodology for human sacrifice in Rome and India at all, of course. I only point out that in each case, when a human sacrifice was imagined the logical ritual practice on which to model it was the sacrifice of a horse. The fact that horses occupied an ontological position that was closer to humans than other animals marked horse sacrifice as the most logical paradigm for human sacrifice. Even without direct relation then, the rituals may still testify to a similar ideological connection between horses and humans, an ideological connection that is a genuine inheritance, and that we have seen in our Greek poetic sources as well.
Horse Sacrifice in Greece
Although this bears no obvious relationship to the PIE ritual, there was perhaps in ancient Greece some connection between kingship and horse sacrifice. These were all kings who were gathered, and the man selected to marry Helen would become the king of Sparta.  Again, we see a continuity of ideology, preserved here in legend rather than in ritual.
Sextus mentions this story in the midst of a condemnation of what he saw as widespread scholarly reluctance to distinguish fact from fiction. Although Sextus mentions this story as if it was a normal topic of discussion among the educated, the obscurity of the other accounts among which it is mentioned may lead us to think otherwise. There are, however, other sources for this story. We find some corroborating data, for example, in Ptolemaios Chennos, who retells some useful pieces of information which, he claims, come from Herodotus:
Finally, we learn from Servius that Odysseus is said to have died when he, still in the form of a horse, was stabbed with a spear.
This particular source is especially tantalizing since the transformation is mentioned here as part of an essential, and fairly minimal, biography of the epic hero, as if this transformation was not terribly obscure to Servius. These scant bits of evidence, however, do not allow us to piece together a mythic narrative, nor even to be certain that they refer to the same story. They may, after all, simply refer to mythical variants linked through the common motif of Odysseus’ equine transformation. Even without an overarching narrative, however, it is still evident that Odysseus was said to have been the subject of equine transformation and that, at least according to Servius, he was sometimes said to have been killed while in horse form, stabbed in a way not dissimilar to Laocoön’s stabbing of the Trojan Horse.
The Horse Sacrifice and the Life of Pelopidas
The sacrifice was then made and the Thebans went on to victory.