I've just started a game with the Zulus. I'm against the Koreans, the Ottomans and the Iroqouis. With my Archers rush, I conquer the Ottomans, and take their capital. Then I move to the Koreans territory and conquer them as well. Now I head to the Iroqouis territory. I come with about 4 archers and 2 impi. I took on one fortified spearman with all my soldiers and they all died. How is this possible? I had the idea that the city was based on a mountain/hill but that wasn't true. What is the solution here? Do I simply upgrade to better soldiers? Or is there some strategy?