Answer:
Civil wars.
Step-by-step explanation:
During the period of the Civil War in the United States, the Union forces formed a blockade of confederate ports intended to discourage the export of cotton and the shipment of war supplies into the Confederacy. Cotton trade was essential for the southern states through which these States exchange war material from foreign nations. The blockade, though quite weak, was a significant economic strategy that effectively stopped the Confederate from getting access to the arms that the developed North could manufacture for itself.