According to my research, the Byzantine strategy for countering eagle warriors in the Castle Age is to use longswords and focus on defensive tactics.
Though longswords are effective against eagles in direct combat, they come with issues related to resources and game meta.
Alternatively, I tested Byzantine pikemen against eagle warriors on a simulation website and found that 16 pikemen can defeat 10 eagle warriors in a head-on confrontation without using gold.
However, I am unsure of the cost-effectiveness of this strategy as the value of gold versus food in the Castle Age for Byzantines is not clear.
I am seeking advice from the community on this matter.
Please note, I mistakenly tested spearmen instead of pikes earlier, which resulted in a 2:1 trade instead of a 1.6:1 trade.