Trade Theatres are a game mechanic in Empire: Total War and an integral component of trading.
Trade theatres are areas in which only naval units may access. In each trade theatre, there are 4-6 circles near the coast where ships may access. Once trade ships (indiamen, dhows, fluyts, and galleons) are in one of the circles in the trade theatres, they establish a trade route running from the circle they are in to the nearest trading port, generating income. The more trading ships are in a trade circle, the more money is generated; however, each additional ship generates less income, and lowers the overall value of all other trade in the commodity. Each trading node can only be occupied by one fleet; fleets of other factions can attack fleets that are operating in the trading nodes. Non-trade ships may occupy a trade area; however, they do not establish trade. Any troops aboard ships in the Trade Theatres may not be dropped off in the Trade Theatres.
Trade Theatres are arenas of contention in the Grand Campaign. Maritime factions such as France, Great Britain. Spain and the United Provinces all pose a threat to each other's trading fleets, and the Pirates patrol almost all theatres at will unless eliminated or otherwise kept in check.
There are four Trade Theatres in the game. There is the coast of Brazil which trades sugar, the Ivory Coast which trades ivory, the coast of Madagascar which also trades ivory, and the East Indies which trades spices.