Yes I was referring to mutalism or rather trade relations that benefited both parties fairly evenly. The stronger these ties, or the larger the trading mutualistic trade relationship, the less likely they are to take up arms against one another. I can't think of any example in history whereby two countries were strongly tied via a mutualistic trade relationship then went to war. I think the Marshal Plan after WWII helps to support this argument in a somewhat different way by saying it helped to maintain an equal trading relationship and not like the Imperialist trade relations (parisitism) that you've mentioned in your comment. I could see someone writing a masters or Phd thesis on such a topic comparing the nuances of biological symbiotic relationships and their corresponding country dynamics and propensity to war.