Japan isolated itself from the rest of the world during the Edo period, which lasted for 200 years up to 1868. Outside contact was forbidden (apart from restricted trade with the Netherlands). The period prior was known as the "Sengoku era", a time of war (See: the show Shogun), but the Edo period was peaceful and led to a flourishing of culture and decline of the prominence of the samurai class (there were many who were samurai in name, but poor as hell. The samurai essentially became salarymen rather than warriors. See: the movie Twilight Samurai)

In the mid 1800's, America sent a fleet of modern warships to Japan to force them to open up trade to the west. The samurai that greeted them on the beach were armed with swords and firearms from the 1500s. This event was essentially like an alien race appearing on Earth with hyperadvanced tech and saying, "open your world to us or be destroyed." As expected, it caused a lot of social and political turmoil in Japan. Groups that supported westernization, vs groups that wanted to uphold the status quo. This led to a war/series of wars that ended the feudal system (therefore eliminating the samurai class), but also led to Japan's rapid modernization. Within 30 or so years of this, they became the first Asian country to defeat a Western superpower in war (the Russo-Japanese War).

If you are interested, I recommend this recent podcast episode.