Commodore Perry (an american commodore), goes to japan and said that they wanted free trade and that they would comeback with more ships when for the japan's decision. The U.S. had much more advanced weaponry to this was a huge threat to the japanese.
China and Britain go to war over Britain selling the narcotic opium to the chinese. (The British wanted to continue trading opium while the chinese government did not want Britain to sell their citizens opium)
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