This strategy was successfully executed on a Diety game so I don't know if it really works or is necessary on the lower levels. I can usually easily keep pace with the Emperor AI but maybe others might find this useful.
The problem I have found on Diety is that there is no way to keep up with the AI research during the Middle Ages. Here's my current tech situation with some civs already at steam power.
Especially in the games I play with at least 7 other civs (large map, pangea 60%, arid, cold, 3 billion) they just move way to fast and it costs way to much GPT to stay even close. So, rather than try to keep up I just accept my fate an wait until the AI reach the industrial age. During the middle ages I completely focus on my economy rush building every improvement that will help me get my gold per turn up and only getting the techs that matter for this like Banking. As you can see from this attached save the year is 640AD and I am researching Chemistry. A quick look at the diplo screens and I'm clearly behind in tech and everyone but Babylon (???) in the industrial age. I have less cities and its looking pretty bleak. However, this is the Civ III AI, so never give up, never surrender.
640AD Researching Chemistry
Now, here is the same game, same YEAR, yes that's right, 640 AD and I'm at tech parity with the rest of the world (the ruskies have communism), have coal and iron which aren't in my borders, I'm bringing in 387gpt (down from 424gpt) and have built my first railroad.
640AD Researching Medicine
How in the name of Sid Meier did I do that?
The scientific trait and Nationalism tech or what I call the Nationalism Slingshot (TM).
In 1.29, the AI totally overvalue Nationalism, to the point where they won't trade it to you normally without way over paying and they don't trade it to one another. We humans don't need to care that much about it and hence our advantage.
So how did I get to nationalism in one turn? I used my built up gpt economy and traded it all to the weakest most picked on AI civ that wasn't scientific, our fan favorite: Joanie. Joanie in this game was a little warmonger and has now started to pay the price. She is being attacked by everyone but the babs and myself. She's in a heap of trouble and I'm here to help.
So here's what I did: I traded all gpt deals with Joanie for Chemistry, Metallury, Physics, Theory of Gravity, and Magnetism. That totalled about 400gpt. This influx of income hopefully will help her stay alive 20 more turns lasting long enough not to sully my rep with her dying. Voila I'm in the industrial age. As a scientific civ Nationalism is a free tech. All the non scientific civs and the babs (who are way behind for some reason in this game) don't have nationalism yet and trade it to them for big bucks and techs. Now my economy is back up, I have coal and iron, and I am at tech parity (that would be all the missing techs on the first shot + monachy and chivalry).
Funny thing is Joanie is lacking Nationalism and Steam Power which I got from one of her enemies. I am able to get 187gpt back from little Joanie by trading Nationalism and Steam power to her. So effectively I'm prolonging the world war against Joanie by pulling as much money as I can from her enemies, giving her rifleman and the draft to help defend her cities and still subsidizing her war effort with 200gpt a turn from her enemies! All this only cost me 37gpt and Nationalism.
I didn't save reload through any of this to find the exact right combination so it might be possible to milk this even more. I'm sure the more experienced Diety players around here could do this much better than I. It also might have been better to hold off on trading Nationalism to some of the civs, but getting steam power, iron and coal is so important I had to leverage it now.
Comments?
The problem I have found on Diety is that there is no way to keep up with the AI research during the Middle Ages. Here's my current tech situation with some civs already at steam power.

Especially in the games I play with at least 7 other civs (large map, pangea 60%, arid, cold, 3 billion) they just move way to fast and it costs way to much GPT to stay even close. So, rather than try to keep up I just accept my fate an wait until the AI reach the industrial age. During the middle ages I completely focus on my economy rush building every improvement that will help me get my gold per turn up and only getting the techs that matter for this like Banking. As you can see from this attached save the year is 640AD and I am researching Chemistry. A quick look at the diplo screens and I'm clearly behind in tech and everyone but Babylon (???) in the industrial age. I have less cities and its looking pretty bleak. However, this is the Civ III AI, so never give up, never surrender.
640AD Researching Chemistry
Now, here is the same game, same YEAR, yes that's right, 640 AD and I'm at tech parity with the rest of the world (the ruskies have communism), have coal and iron which aren't in my borders, I'm bringing in 387gpt (down from 424gpt) and have built my first railroad.

640AD Researching Medicine
How in the name of Sid Meier did I do that?
The scientific trait and Nationalism tech or what I call the Nationalism Slingshot (TM).
In 1.29, the AI totally overvalue Nationalism, to the point where they won't trade it to you normally without way over paying and they don't trade it to one another. We humans don't need to care that much about it and hence our advantage.
So how did I get to nationalism in one turn? I used my built up gpt economy and traded it all to the weakest most picked on AI civ that wasn't scientific, our fan favorite: Joanie. Joanie in this game was a little warmonger and has now started to pay the price. She is being attacked by everyone but the babs and myself. She's in a heap of trouble and I'm here to help.
So here's what I did: I traded all gpt deals with Joanie for Chemistry, Metallury, Physics, Theory of Gravity, and Magnetism. That totalled about 400gpt. This influx of income hopefully will help her stay alive 20 more turns lasting long enough not to sully my rep with her dying. Voila I'm in the industrial age. As a scientific civ Nationalism is a free tech. All the non scientific civs and the babs (who are way behind for some reason in this game) don't have nationalism yet and trade it to them for big bucks and techs. Now my economy is back up, I have coal and iron, and I am at tech parity (that would be all the missing techs on the first shot + monachy and chivalry).
Funny thing is Joanie is lacking Nationalism and Steam Power which I got from one of her enemies. I am able to get 187gpt back from little Joanie by trading Nationalism and Steam power to her. So effectively I'm prolonging the world war against Joanie by pulling as much money as I can from her enemies, giving her rifleman and the draft to help defend her cities and still subsidizing her war effort with 200gpt a turn from her enemies! All this only cost me 37gpt and Nationalism.
I didn't save reload through any of this to find the exact right combination so it might be possible to milk this even more. I'm sure the more experienced Diety players around here could do this much better than I. It also might have been better to hold off on trading Nationalism to some of the civs, but getting steam power, iron and coal is so important I had to leverage it now.
Comments?