Re: chain armour
Chain mail is excellent against slashing attacks but less so against projectiles/thrusting attacks. Given how spears were the most common armament of Chinese footsoldiers it is no surprise that chainmail didn't catch on. Besides it is just too time consuming making chain mail any ways.
There is nothing surprising at all. China armour had been imported into China in 718. Not widely used, but that doesn't mean ancient China do not have it. China have been actively trading with countries like Persia and Rome since ancient time.
Plus chain armour do not originated from Persia. It was introduce to asia by the Roman.
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Chain mail is excellent against slashing attacks but less so against projectiles/thrusting attacks. Given how spears were the most common armament of Chinese footsoldiers it is no surprise that chainmail didn't catch on. Besides it is just too time consuming making chain mail any ways.