If you decide that anyone who trades or gives aid to someone you declare war on is an enemy then you will ofc end up warring nearly every faction by default
I'm not trying to be a victim here but, giving troops to attack someone OR attacking caravans completely out of your own border is a very hostile move. Then like all things with a real life diplomacy, the "victims" can chose to declare war or just make it a skirmish and dont push casus belli, but if all was fair and just, it would instantly mean being added on the warlist
Its one of the most interesting elements of diplomacy : the void between neutral and hostile, and the void between hostile and actual war. You can use a lot of arguments to go from one to the other in the space of an heartbeat, if you think you can benefit from it