When I used to play the TW series -- indeed, emphasize 'used to' -- I commonly blockaded ports and sabotaged marketplaces (as well as as many enemy buildings as possible). I also declined any trade offer from a soon-to-be foe to withhold them any fruit from it that could aid them. And I also wished there were a way to diplomatically cease a foe's trade agreements with other factions. Sending in spies to cause dissatisfaction among their settlements and the use of assassination were two of my favourite tools.