Is Darius doing something I'm not aware of?

[Full Metal]

He declared war on me around turn 85, and his troops have been able to run thru forests for more than 50 turns.

Is he doing something to get them to have their +1 move, even without a GA? If so, I'll have what he's having!

 

[Light Cleric]

The AI has so much excess Happiness that it's very easy for them to be in Golden Ages, combined with his UA making them go 50% longer, plus the possibility of Chichen Itza and the Golden Age granted by Representation if he went Liberty.

This is why I hate dealing with Darius in the early game.

 

[Biologist]

This is why I hate dealing with Darius in the early game.

Indeed, if I encounter Darius early on and he is anywhere within marching distance of my capital, he becomes a priority for invasion. I always try to archer rush Darius before he can get off an Immortal spam. Depending on the game speed and difficulty level, it's possible that Darius simply got a Golden Age that early, then kept it going with policy bonuses.