Laudator Temporis Acti

Xenophon, Anabasis 3.2.11-12 (tr. Carleton L. Brownson, rev. John Dillery):

For when the Persians and their followers came with a vast array to blot Athens out of existence, the Athenians dared, unaided, to withstand them, and won the victory. And while they had vowed to Artemis that for every man they might slay of the enemy they would sacrifice a goat to the goddess, they were unable to find goats enough; so they resolved to offer five hundred every year, and this sacrifice they are paying even to this day.

ἐλθόντων μὲν γὰρ Περσῶν καὶ τῶν σὺν αὐτοῖς παμπληθεῖ στόλῳ ὡς ἀφανιούντων τὰς Ἀθήνας, ὑποστῆναι αὐτοὶ Ἀθηναῖοι τολμήσαντες ἐνίκησαν αὐτούς. καὶ εὐξάμενοι τῇ Ἀρτέμιδι ὁπόσους κατακάνοιεν τῶν πολεμίων τοσαύτας χιμαίρας καταθύσειν τῇ θεῷ, ἐπεὶ οὐκ εἶχον ἱκανὰς εὑρεῖν, ἔδοξεν αὐτοῖς κατ᾿ ἐνιαυτὸν πεντακοσίας θύειν, καὶ ἔτι νῦν ἀποθύουσιν.

6400 Persians were slain at Marathon (Herodotus 6.117).

Plutarch, On the Malice of Herodotus 26 (Moralia 862 B-C; tr. Lionel Pearson):

They say that the Athenians promised Artemis Agrotera that they would sacrifice a goat to her for every barbarian killed; and then, after the battle, when the immense number of the dead became apparent, they passed a resolution asking the goddess to release them from their vow on condition that they sacrificed five hundred goats every year.

φασι τοὺς Ἀθηναίους τῇ Ἀγροτέρᾳ θύσειν χιμάρους ὅσους ἂν τῶν βαρβάρων καταβάλωσιν, εἶτα μετὰ τὴν μάχην, ἀναρίθμου πλήθους τῶν νεκρῶν ἀναφανέντος, παραιτεῖσθαι ψηφίσματι τὴν θεόν, ὅπως καθ᾿ ἕκαστον ἐνιαυτὸν ἀποθύωσι πεντακοσίας τῶν χιμάρων.

N.G.L. Hammond, "The Campaign and the Battle of Marathon," Journal of Hellenic Studies 88 (1968) 13-57 (at 40-41, footnotes omitted):

The moon-goddess held an important place in the religious associations of the battle. The commemorative coins struck from 490 B.C. onwards showed a waning moon behind the owl of Athena; and an annual thanksgiving for the victory was made in honour of Hecate Agrotera or Artemis Agrotera as the moon-goddess, the huntress, at her already established festival at Agrae, which was held on the 6th of Boedromion, that is some eleven days before the actual battle of 490 B.C. Seltman and others have thought the waning moon was added to give the date of the battle. But as the thanksgiving to the moon-goddess for victory was divorced from the date and as a waning moon is a vague way of defining a date, one wonders if the date per se had any special or religious importance. It is more likely that the moon-goddess played an important part in the victory and that the χαριστήρια τῆς νίκης were paid to her for her part in it; and that the waning phase, shown on the coins, was a particular factor in the victory. We may envisage the situation. Each night before full moon, as moonset drew nearer to sunrise, the Persian cavalry returning near moonset arrived later and the interval of darkness before sunrise dwindled; then, when it was full moon, moonset was half an hour before sunrise and the cavalry returned shortly before dawn; on the following night the moon set after sunrise, and the cavalry had not returned by dawn—were perhaps already on the way back—when 'the Athenians were let go and rushed at speed upon the barbarians' (Hdt. vi 112.1). The state-festival, led by the polemarch (Ath.Pol. lviii 1), in thanksgiving to the moon-goddess would thus have a particular explanation. Aristophanes Eq. 660 mentions the sacrifice to the huntress goddess, Agrotera, and Xenophon, Anab. iii 2.12, explains its connection with Marathon as follows: 'The Athenians, having vowed to Artemis to sacrifice as many goats to her as they killed of the enemy, when they could not find enough, resolved to sacrifice five hundred every year; and even to this day they offer sacrifice in thanksgiving for that victory.' The decree of the Athenian state is mentioned also by Plutarch, de malign. Herod. 26.7 = Mor. 8 [sic] (τοὺς Ἀθηναίους ... ψηφίσματι). The official spokesman of the vow by the Athenian state was probably the archon polemarchus, just as the official who conducted the sacrifice at the festival was the archon polemarchus (Pollux vii 91). On the 6th of Boedromion in 490 B.C. the archon polemarchus was Callimachus, and the Scholiast to Arist. Eq. 660 may be correct in stating that Callimachus made the vow. If so, the vow was made on the 6th of Boedromion in his year of office, 490/489 B.C., and in his lifetime, so that the battle was fought not before that date, e.g. in Metageitnion, but later in Boedromion. I suggest then that at the established festival of Artemis and Apollo on the 6th of Boedromion in 490 B.C., when Eretria had fallen and in fact two days before the Persian landing at Marathon, the Athenian state made this vow; and that, when the moon-goddess played her part later in bringing victory at Marathon, the thanksgiving was made to her in perpetuity, and she took precedence over Apollo in the cult thereafter.

Robert Parker, Athenian Religion: A History (Oxford: Clarendon Press, 1996), p. 153 (footnote omitted):

Xenophon tells us that, again before Marathon, the Athenians vowed to sacrifice to Artemis Agrotera one goat for every Persian slain. So vast was the slaughter that, for want of goats, they commuted the vow to an annual offering of 500, but in that form it was still carried out in Xenophon's day, and the procession to Artemis' shrine survived in Plutarch's. (A cult of Zeus Tropaios at the site of the battle also commemorated the victory more directly.) This spectacular rite—the earliest attested instance, incidentally, of the great democratic institution of the 'public feast', δημοθοινία—must have enhanced the fame of Artemis Agrotera, and it was perhaps she who was honoured (in the 440s?) with the elegant Ionic temple beside the Ilissus which Stuart and Revett were still able to capture in a drawing in the 1750s.