Chainmail and Last minute Preparation
Chainmail was a superb type of armor made of interconnected steel rings that provided very good protection from sword, spear, and arrow strikes.
This type of armor had not been invented yet and it was also not something that was going to be used in the upcoming battle as it was too time-consuming to make a lot of in the short time they had.
On the contrary, this was more of a pet project of Alexander, as he wanted to have the presumably the best blacksmiths in the country try their luck on making this very good, but also prohibitively time-consuming piece of armor.
He wanted to see how viable it was to make such armor with the existing technology and the unforeseen challenges that existed.
So, he got a few blacksmiths together and first showed them the basics he had learned while he was working for a prop company sometime earlier in his previous life.