Calchas, seer of the Achaeans from Aulis to the Trojan War
Calchas, son of Thestor and seer of the Achaean army: the portent at Aulis, the sacrifice of Iphigenia, Apollo's anger and his contest with Mopsus.
In the army that sailed for Troy, alongside kings and warriors, there was a man whose authority did not come from weapons. Calchas, son of Thestor, was the seer of the Achaeans. The Iliad introduces him in its first book with a famous formula: he knew the things that are, that will be and that were before, and through the prophetic art given him by Apollo he had guided the ships to the Trojan shore.
The portent at Aulis
Calchas' first great prophecy dates from the gathering of the fleet at Aulis, in Boeotia. In the second book of the Iliad Odysseus reminds his companions of it: during a sacrifice by a spring, a serpent emerged from beneath the altar, devoured eight sparrow chicks in a nest and finally their mother, and was then turned to stone by Zeus. Calchas interpreted the sign: the war would last nine years and Troy would fall in the tenth.
More dramatic is the episode that the tragic tradition links to the same halt. When contrary winds prevented departure, the seer declared that Artemis, offended, demanded the sacrifice of Iphigenia, Agamemnon's daughter. Aeschylus in the Agamemnon and Euripides in Iphigenia at Aulis gave the story different shapes; in some versions the girl was saved at the last moment by the goddess and replaced on the altar by a deer.
Apollo's anger and the clash with Agamemnon
The Iliad opens with a plague that ravages the Achaean camp. Achilles summons the assembly and asks for a seer to explain its cause. Before speaking, Calchas asks for protection, because he knows the truth will anger the king. He reveals that Apollo is punishing the Greeks for the insult done to his priest Chryses, whose daughter Chryseis was being kept by Agamemnon as a prize of war.
The king's reaction is immediate and violent: he accuses Calchas of never having foretold anything pleasant to him. The episode shows clearly the ambiguous position of the ancient seer, indispensable to command yet exposed to the wrath of the powerful. From that revelation springs the quarrel between Agamemnon and Achilles, which drives the entire poem.
The contest with Mopsus
Later sources also tell of the seer's end. According to an oracle, Calchas would die when he met a seer more skilful than himself. After the war he came to Claros, near Colophon, where Mopsus, son of Manto, lived. Strabo, citing a Hesiodic tradition, reports the contest between them: Calchas asked how many figs a tree bore, and Mopsus gave the exact number and even the measure they would fill.
In another variant the contest concerned a pregnant sow and the number of her young. Either way, Calchas, defeated by his rival, is said to have died of grief. The story expresses an idea dear to the Greeks: even prophetic wisdom has its hierarchy, and every seer carries within him the limit of his own knowledge.
The name of Calchas remained tied to the image of the military seer, interpreter of sacrifices and the flight of birds in the service of an army. Dante recalls him in the twentieth canto of the Inferno as the one who, with Eurypylus, gave the signal to cut the cable of the first ship at Aulis, and his figure continued to appear in the Trojan poems of the Middle Ages and the Renaissance.