What are some of the good that one country would not want its enemy to import during a war

The obvious answers would be weapons, supplies, foreign soldiers, food, horses, etc.
If there is a war going on between two or more countries, obviously they wouldn't want their enemies to thrive and prosper during such an event. If an enemy country manages to import these goods during a war, then the war will only be prolonged, which is something no one wants.

The used coins.. .