#Before I say anything, I haven't read the manga so please don't spoil anything and remember to use spoiler tags.
When I was watching episode 5 of this season I noticed that Marleyan soldiers from 2000 years ago were wearing Roman helmets.
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In real life, the Roman Republic was at war with Iranian empires from 54 BC to 628 AD ( source: https://en.wikipedia.org/wiki/Roman-Persian_Wars ), so, it started about 2000 years ago.
Another thing that happened 2000 years ago in Iran was the migration of Aryans ( source: https://iranologie.com/the-history-page/the-land-of-iran-… ) "Linguistically, Iran means the land of the Aryans, the eastern branch of Indo-Europeans. A group of Aryans (or Indo-Iranians) who migrated to the Iranian plateau around 2000 BCE from Central Asia".
I've seen some people saying the Eldian race is an analogy for Nazis but I don't think that's quite right, I think the Eldian race is an analogy for the Aryan race, Aryans migrated to Iran 2000 years ago the same way Eldians migrated to wherever Ymir's village was 2000 years ago, and they fought Marleyans who look very much like the Romans the Iranian empire fought.
Also, Eldians look kind of similar to ancient Iranians.
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You can also find some interesting information here:
https://www.quora.com/What-did-ancient-Persians-physicall…
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