Létoublon, Françoise. 2023. “Palamedes and Letters: A Hero and Martyr in the Trojan War.” In “Γέρα: Studies in honor of Professor Menelaos Christopoulos,” ed. Athina Papachrysostomou, Andreas P. Antonopoulos, Alexandros-Fotios Mitsis, Fay Papadimitriou, and Panagiota Taktikou, special issue, Classics@ 25. https://nrs.harvard.edu/URN-3:HLNC.ESSAY:103900175.
1. Palamedes in the Cypria
It may seem difficult to build a hero from those short mentions, but as they are complemented with several details found throughout Greek literature, they help us draw a more precise story.
Hyginus provides even more details on Odysseus’ device: he put on a cap, pretending madness, and yoked a horse and an ox to the plow. 
2. Palamedes’ death: A thrilling blockbuster
2.1. “Illiterate” versions
This death by fishing might have been the subject of a vase black-figure painting of the sixth century which has been interpreted as representing Palamedes’ ghost seeking vengeance.  This version is arguably an early one, especially since Pausanias explicitly says that he drew it from the Cypria.
So does Dictys’ Ephemeris of the Trojan War, a novelistic pseudo-diary allegedly composed day-by-day  :
2.2. A (fake) letter
Let us note in this text the enumeration of Palamedes’ deeds for the Greeks (ὤνησε τὸν Ἑλληνικὸν λαόν): he cured the famine at Aulis through a seamless (ἀνεπίληπτον) distribution of food, the teaching—rather than the invention—of Phoenician letters (τὰ Φοινίκια διδάξας γράμματα), the discovery of measures and pebbles (used for reckoning). Palamedes’ reputation made Agamemnon, Odysseus, and Diomedes jealous, which explains the plot against him; i.e. a Phrygian captive was forced to write a letter in the Phrygian alphabet,  “as if it was from Priam to Palamedes,” and then he was put to death, while an attendant of Palamedes placed the tablet with the Trojan gold under Palamedes’ cot. Palamedes was accused of treason and his tent was searched; once the tablet and the gold were found, Palamedes was killed by stoning. His father, Nauplius, took revenge (as probably narrated in the Nostoi of the Epic Cycle).
In a note to his translation, Frazer speaks of a “Machiavellian device”;  Gantz remarks that Apollodorus’ version, “too brief to add much to this,” has Odysseus act alone, like Hyginus.  This is what Hyginus says in his Fabulae: 
Although different authors give different accounts of Palamedes’ death and of the devices used to kill him (using a fake letter or not), they all incriminate Odysseus’ jealousy and hatred against Palamedes,  be Diomedes implied in the plot or not. Another striking feature is the presence of a trial, giving Palamedes a voice and a possibility to defend himself (or not  ); in the case of a trial, he was condemned to die by lapidation.
3. Palamedes’ apology
3.1. Palamedes in the early period of the war
3.2. Palamedes as πρῶτος εὑρετής
ἐξηῦρον αὐτοῖς γραμμάτων τε συνθέσεις,
μνήμην ἁπάντων, μουσομήτορ᾽ ἐργάνην.
Thus, numbers and letters—precious for memory, and hence for the Mousai—would appear to be Palamedes’ invention rather than Prometheus’.
σταθμῶν, ἀριθμῶν καὶ μέτρων εὑρήματα
τάξεις τε ταύτας οὐράνιά τε σήματα.
κἀκεῖν᾽ ἔτευξε πρῶτος, ἐξ ἑνὸς δέκα
5 κἀκ τῶν δέκ᾽ αὖθις ηὗρε πεντηκοντάδας
καὶ χιλιοστῦς, καὶ στρατοῦ φρυκτωρίαν
ἔδειξε κάνέφηνεν οὐ δεδειγμένα.
ἐφηῦρε δ᾽ ἄστρων μέτρα καὶ περιστροφάς,
ὕπνου φύλαξι πιστὰ σημαντήρια
10 νεῶν τε ποιμαντῆρσιν ἐνθαλασσίοις
ἄρκτου στροφάς τε καὶ κυνὸς ψυχρὰν δύσιν.
And it was he who devised the wall for the army of the Argives;
his was the invention of weights, numbers and measures;
he taught them to marshal armies thus and how to know the heavenly signs.
He was the first, too, who showed how to count from one to ten and so to fifty
and to a thousand; he showed the army how to use beacons,
and revealed things that earlier were hidden.
He discovered how to measure terms and periods of the stars,
trustworthy signs for those who watched while others slept,
and for the shepherds of ships at sea he found out
the turnings of the Bear and the chilly setting of the Dogstar.
As far letters are concerned, it is sometimes questioned whether he had invented or rather adapted them,  and in the latter case, if the model was the Phoenician characters: if so, Palamedes would have invented the Greek alphabet out of syllabic writing. Phillips aptly remarks  that the various uses of the letters mythically attributed to Palamedes in Euripides’ fragment 578,  are historically known for Mycenaean writing, leading him to conclude: “Thus there seem to be grounds to supposing that Palamedes is a figure that represents, in some sense, many characteristic achievements of the Minoan civilization as inherited and developed by the Mycenaean Greeks.” 
We do not know of any visual representation of this very scene, but a beautiful black-figure painting signed by Exekias shows Achilles and Ajax playing a board game.  Both images, by Exekias and by Polygnotos, might recall that Palamedes’ invention of such games aimed at entertaining the warriors during the dead time between fighting, according to Sophocles fr. 479. 
3.3. From the alphabet to letters and fakes or Palamedes tragicus
3.4. Palamedes as sophist?
So much so that Palamedes, clashing with a liar, plotter, and betrayer Odysseus, appears himself one of the sophists. At least, both of them may be equally considered as such, taking the risk of being condemned by philosophers.
4. The erasure of Palamedes from the Iliadic tradition? 
According to Protesilaos, who tells the story to a vine-dresser, Palamedes could vie with Achilles for the title of the “Best of the Achaeans”; yet Odysseus, having treacherously killed Palamedes, negotiates with Homer himself the entire annihilation of his achievements and even his name: that is why he never appears in the Iliad.
One could argue however that, since Palamedes died before the beginning of the tenth year of the war, when the Iliad begins, it is normal not to meet him in the poem’s timespan. Nevertheless, the Iliad mentions a fair number of characters who died before the plague sent by Apollo to the Achaeans (as a punishment for Chryseis detained by Agamemnon), as well as many deeds accomplished before that episode. Palamedes’ story is somehow a taboo, maybe not as explicitly as the Palladion was.  Of course, it was not Odysseus’ will that occasioned Palamedes’ erasure, as the abovementioned ancient authors state—no matter how appealing the anecdote about Odysseus negotiating this disappearance with Homer may appear—but it seems clear that the Iliad is already pro-Odyssean, whereas Dictys and Philostratus are anti-Odyssean, following Oiax’ and Nauplius’ arguments, and thus charging Odysseus perhaps with more crimes than he committed. Palamedes’ story perhaps reveals that literature, far from being politically neutral, testifies to political leanings as early as the Homeric epic. Of course, this phenomenon is quite explicit and most common in the classical and postclassical periods (think of Plato, Demosthenes, and Aeschines, for instance), but it is somewhat surprising when this occurs in the epic; yet here there is an obvious contrast between the Iliad and the Epic Cycle tradition. Just like some references to the Antenorids may refer to a conflict inside the Trojan camp,  several strifes and conspiracies may have also swirled the Achaean camp, apart from Achilles’ wrath, conducing to the fundamentally political nature of the Iliad, as shown by Hammer (2002).
τὰ τῆς γε λήθης φάρμακ᾽ ὀρθώσας μόνος,
ἄφωνα και φωνοῦντα, συλλαβὰς τιθείς,
ἐξηῦρον ἀνθρώποισι γράμματ᾽ εἰδέναι,
ὤστ᾽ οὐ παρόντα ποντίας ὑπὲρ πλακὸς
τἀκεῖ κατ᾽οἴκους πάντ᾽ ἐπίστασθαι καλῶς,
παισίν τε τὸν θνῄσκοντα χρημάτων μέτρον
γράψαντα λείπειν, τὸν λαβόντα δ᾽ εἰδέναι.
ἃ δ᾽ εἰς ἔριν πίπτουσιν ἀνθρώποις κακά,
δέλτος διαιρεῖ, κοὐκ ἐᾷ ψευδῆ λέγειν.
εἰπεῖν, χρόνου τε διατριβὰς σοφωτάτας
ἐφηῦρε φλοίσβου μετὰ κόπον καθημένοις,
πεσσοὺς κύβους τε, τερπνὸν ἀργίας ἄκος;
ἀλλὰ καὶ ἀντιθέῳ Παλαμήδεϊ θῆκας ὄλεθρον
ὅς σέο φέρτερος ἔσκε βίῃ καὶ ἐύφρονι βουλῇ.
“You also managed to get godlike Palamedes killed,
a man superior to you in both strength and wise counsel.” (transl. Hopkinson 2018)
On the “denigration” of Odysseus, see Stanford 1949.