
Originally Posted by
RGA
As strangely as it might sound, your land army was perhaps too far away to reinforce. Because the city itself is so big, two armies camping at two opposite ends of it might be well outside the zone of control of each other, thus unable to help when the other is attacked. The Zone of control mechanics is quite buggy with sieges. I once suffered from an annoying exploit by AI: I had one big army camping outside a city. AI first besieged the city with an one-unit-stack, while concentrating all of its remaining force against my army. As my city was under siege, it could not reinforce. Really really annoying.