Sometime in the sixteenth year of Xerxes great king (circa 468/7 BCE in our calendar), someone at Persepolis turned a tablet with Elamite writing on end and rolled his seal along it. A conversation with Josho Brouwers of Karwansaray BV recalled it to memory. Because this seems to show the style of body armour with a tall neck-guard and flaps over the shoulders which is often understood as distinctively Greek and said to have been invented about a hundred years before Xerxes based on its appearance in Greek vase paintings. But there is no hint of the Aegean in this scene, and this armour is missing the skirt of pteryges around the waist which usually appear in depictions of armour with this cut from the Aegean.
Showing where this style of armour was invented and how it spread and changed is more difficult than it sounds. It is true that the earliest evidence is painted pottery from mainland Greece in the early sixth or perhaps the late seventh century BCE. But in the sixth century BCE, it happens that we have much more evidence for arms and armour from the Aegean than from anywhere in the neighbourhood. The people there painted armoured men on their pots with durable glazes and carved them on stone, and they deposited large amounts of armour and weapons in graves and especially temples. So it is very dangerous to say that the Greeks invented an object just because it is first depicted in the Aegean, especially if that object is one which does not survive well in the ground. It is usually thought that the first armours with this cut were of cloth or felt or hide, and none of those materials survives 2500 years in the ground unless the conditions are just right. Although by the second century BCE armour with this cut was being worn all around the Mediterranean and made in every possible material, not a single fragment made from cloth or hide has been identified. So while this style of armour was probably invented somewhere in or near to the Aegean around the sixth century BCE, its hard to say for sure that it was invented by Greeks.
Whoever invented this style of armour, from the fifth century onwards it seems to have spread east and west with Greek and perhaps Etruscan and Phoenician sailors and soldiers and artisans. Yet its a bit harder to say how the people who borrowed it understood what they were doing.
If we look at the Darius Mosaic from Pompeii, an incredibly good copy of a painting made circa 300 BCE, we see this style of armour on both sides. The Persians desperately defending their king mostly wear armours with this cut but with a blocky shape and red surface. The king of the Macedonians who are pushing into the scene from the left as Darius’s driver turns away also wears this style of armour, but his is different in almost every detail. Clearly Macedonians and Persians adapted the basic form of this armour to their own taste. While Greeks liked to boast that Philip of Macedon had borrowed his phalanx from Homer, and Darius and his men had copied Greek swords and lances, no Macedonian or Persian has left us their words to tell us whether they saw their armour as Greek. And the soldier on the seal above was happy to wear close-fitted Iranian clothing under his armour, thrust a very Iranian axe behind his shoulder where he could grab it quickly, and leave aside the large round shield which warriors from the Aegean favoured for hand-to-hand combat.
Further Reading: Duncan Head, The Achaemenid Persian Army (Montvert: Stockport, 1992) p. 27 fig. 14a, John Curtis and Nigel Tallis eds., Forgotten Empire: The World of Ancient Persia (University of California Press: Berkeley, 2005) pp. 210-217. The Oriental Institute Publications on Persepolis are free and well worth the reading (link).
Edit 2022-03-12: Fixed formatting broken when WordPress introduced the block editor