How would today’s technology prevent a “union blockage” from being successful?

Union blockage came into existence in America intending to block trading during the civil war. The goal was to prevent necessary supplies from reaching the confederates since the army felt that if the war lasted for a long time, the best supplied military would win the battle.  

In the recent years, technology has changed international trade massively and has also reduced other trade wars and addressed international tariffs. Union blockage could be prevented by the use of methods that help identify shipping containers easily.

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