Uranium hooked up, not getting it

[LlamaCat]

Seems I've seen threads with similar problem before and I have this in my current game so I'll dredge it up again for some possible explanations:

Playing 2.08 Warlords as Korea: I had uranium hooked up, but no oil (yet) .. it was on a mined hill right next to one of my cities, with a road. All my cities are connected by the trade network (this is like the late 1700s or whatever). I have the tech to build destroyers and transports (Combustion) yet for some reason the game will not let me build these two units..? The game clearly says that they require oil OR uranium, so what gives? Later when I got my source of oil hooked up... yep, I could build destroyers and transports.

Keep in mind too that I did have Physics researched and the uranium obviously was revealed. So I don't know what else could be the explanation unless it would be a bug, which doesn't seem likely on my system and with the patch.

 

[DaveMcW]

Uranium mines do not function until you discover Fission.

 

[LlamaCat]

aha! thanks so much.... well that's a much easier answer than I expected. I'm not sure if this is explained in the game anywhere but it's good to know - it always seems a little confusing and strange to me that certain resources are discovered with one tech but you can't use them until another tech - not always sure what the point is.
I was basing my whole strategy of this game on having a strong early navy to guard my coasts since I was isolated by a continent on three sides, then going for space race victory. My only source of oil was just outside my borders for many years but the uranium popped up earlier.