in my games the ai actually seems to become weaker when they reach about the atomic age or so. the reason i believe is because they begin building atomic bombs, which convinces them that they are really really strong based on the demographics screen, even if their ground/air/naval forces are almost nonexistent.. not to mention the production time spent building atomic bombs. recent game theodora had an entire continent to herself after conquering a few others. in the diplomacy screen she had hundreds of thousands of gold and gpt was crazy. the demographics screen told me her forces were about 8 times the size of mine. i brought a couple aircraft carriers, full of bombers, a couple battleships and a few riflemen and found her continent almost entirely undefended. i didn't see a single ship, no airforce, just a few scattered modern infantry and rocket artillery, which she threw at me willy nilly and were picked off easily. after taking her capital and several of her top cities i made it to the other side of the continent to find she had a puppeted spanish city with about 20 atomic bombs just sitting there.. which she never ended up using on me.