There are a number of issues here, with a lot of the equipment for the Yeoman being ahistorical to the specified period in the battle and because the obvious disparity in metallurgy. The Persians are given bronze scale mail, which puts them at a massive material disadvantage when compared to the steel chainmail used by the Yeoman (Which the author horrendously misrepresents in the battle).
When it comes to the Yeomans equipment, the Yeoman is carrying 2 weapons which didn't exist during the time he's specified to be from. The battle states that the Yeoman were from the 3rd crusade and serving under Richard the Lionheart, which happened in the 12th century. This makes the inclusion of the Rondel and Bastard sword improper, with both weapons not used until the 14th century.