The modern clash between East and West began in earnest in 1853, suggests George Feifer, when Commodore Matthew Perry landed in Japan, intending to frighten the Japanese into submission. Due to his careful preparation and gunboat diplomacy, he succeeded; an unequal treaty was signed at Kanagawa, which opened ports to America and ended centuries of Japanese isolation. Both sides believed they were morally and culturally superior to the other, and misunderstandings and distrust would persist far into the 20th century. Admiral Yamamoto Isoruku, the mastermind of the Pearl Harbor attack, once said that he had joined the Navy because he «wanted to repay Commodore Perry's visit.»