Answer :
Answer:WW2 or Cold War?
Explanation:
It depends if this is before or after WW2, if it is it will be since they didn't want their enemies to get supplies thus squeezing off their resources and essentially starving them. If it is afterwards it might be because the Cold War?
Answer:
Countries began to make trade blocs in the 1940's due to the War. The more countries put restrictions on who and where they could trade with, the less supplies their enemies would have. Also, countries like the United States did not want to get involved, and trade blocs were legalized, defensive ways of remaining uninvolved.