# Combined Catan player+player+bank transactions

Consider the following Catan scenario:

• Player A has 3 wheat. Wants ore.
• Player B has 1 wheat + 1 ore. Wants brick.

Question: Is there any official rule which would explicitly explain if the following trade is legal or not?

• Player B agrees to give 1 wheat + 1 ore, if he gets 1 brick in return.
• Player A doesn't have brick yet, but he gets his fourth wheat from player B. Immediately exchanges 4 wheat to 1 brick in bank. Gives brick to B.

Note, that this is not equivalent to:

• Player A gives 3 wheat for 1 ore.

...because, in this case, player B ends up with 4 wheat, not 1 ore. (He may still exchange wheat for ore in his turn, but until such time, he has more resources.)

No, this is not legal as written. This is really a series of three separate trades (one of them being with the bank), and two of them are giving a resource for free, which is forbidden by the rules.

The problem is that a trade can only involve 2 people, so a "triangular trade" must be done as separate trades. From the FAQ:

Trade - Is a “triangular trade” permitted? On player A’s turn, are player B and player C allowed to trade with each other if afterwards one of them uses the obtained resource for trading with player A?

No. Not only is a triangular trade forbidden, it is also unnecessary, because player B and player C each trades individually with player A and, thus, may trade whatever resource he has – provided that it meets the requirements of player A.

And:

Trade - May I give away resources or buy services with them, for example, to avoid being bothered by the robber?

No. On Catan, a trade always involves giving and taking resources. Consequently, Catan’s trade law does not contain a “trade” of something for nothing or for immaterial goods such as services.

If they really want to do this, and they trust each other, they can do the following trades:

1. A gives 3 wheat and gets 1 ore
2. B gives 4 wheat and gets 1 ore
3. A trades 4 wheat to the bank for 1 brick
4. A gives 1 brick and gets 1 ore

Those are 4 separate, legal trades that have the same result. But there's nothing stopping either player from choosing to stop after any given step; though doing so will hurt their chances of being trusted in future trades and even future games.

• Thanks! This is what I suspected after I read the "triangular trade" entry in the FAQ. However, I was only 99% sure. I guess I would be more confident if the FAQ would include an explicit sentence saying "Same applies to trading with the bank." Commented Apr 23, 2017 at 19:40
• @wrygiel Good point. But to the best of my knowledge, there is no rules differentiation between trading with the bank and trading with another player; any rules that apply to trading apply to both. The bank just acts as a player who is always willing to make a specific kind of trade. Commented Apr 23, 2017 at 20:26