I'm writing a novel in which an isolationist republic has to open its borders following a series of volcanic eruptions in its territory that destroyed most of the crops and coal mines (the republic is currently in the industrial era). This nation can no longer feed its population because of the bad harvests and is in serious need for more coal to power its industries, so it has to open up trade with its neighbours.
I'd like to ask how would this republic go about it? Send messengers to every nation close to it, invite representatives and ambassadors to the capital, etc., or simply open the borders and let the traders in without involving foreign politics?
This is a big plot point in the story. Until now, I assumed diplomats and ambassadors would be invited into the capital for a tour and establishment of diplomatic relations. Is this how nations in our world opened up after a long period of isolation? If not, what is? Or is it hard to say and up to my judgement?