Projects & units w/o requirements: How did the AI do that?!

[BasiliskPie]

Civ4 (latest download) at Noble lvl:Three times, recently, I've found the enemy AI doing things I can't explain: [Germany] building Three Gorges Dam [3GD] w/o a req. tech.; AI's twice owning serious numbers of military units w/o req. techs, etc. [E.g.: lots of SAM's w/o rocketry.]

I could explain the unjustified units IF I believed the AI's were exchanging units and the poor-tech country was receiving aid from an ally... which I guess is legit but I've never noticed before. Does this happen? But building 3GD w/o [Plastics, or whaddevah]? I think the Germans were also doing Apollo w/o something req'd.

One explanation -- but News To Me if this is true -- would be that entering a trading mode doesn't disclose ALL technologies? Or do vassals have some tech-sharing ability? [Only saw the concept of "vassals" for the first time a few minutes ago while skimming the FAQ... need to read more closely.]

Well, that 3GD game had a lot of puzzles. I expect there's some rational explanation for all this as I'm no Expert. 'Just found the FAQ and I'll have to read that in detail as it looks like it could seriously improve my game if I learn it. Thanks... and sorry if this is already posted in some manner, but I couldn't think of a search-phrasing which would show it.

[MrCynical]

When in diplomacy it only shows those of your opponent's techs that you have the prerequisites for, and hence are allowed to trade for.

If for instance, you don't have the prerequisite techs for rocketry (say you're missing artillery), it won't display Rocketry in the diplomacy panel, even if your opponent has it.

[BasiliskPie]

Good grief... been playing this for ages and never knew that. 'Bet that explains a lot of minor surprises over the past year[s?]. Sigh.

Many thanks.

Edit: As I think about it... I wonder why the untradable tech's aren't displayed-but-locked [as when the country refuses to trade things]... that makes more sense to me and is what I'd have expected.

[Bushface]

It works just the same in the other direction: if you have a tech for which an AI civ does not have the prerequisites, that tech won't appear in the display of techs you could trade to that civ.

[CivMonger]

and I believe if you trade for one of those prereqs you can't get the next tech until the next turn.

[3 EMS]

Originally Posted by BasiliskPie

Good grief... been playing this for ages and never knew that. 'Bet that explains a lot of minor surprises over the past year[s?]. Sigh.

Many thanks.

Edit: As I think about it... I wonder why the untradable tech's aren't displayed-but-locked [as when the country refuses to trade things]... that makes more sense to me and is what I'd have expected.

Sometimes a tech advantange can be very lopsided and listing the techs, wether tradeable or not, could mean listing nearly the entire tech tree.