Japan was not like the other nations of East Asia when it came to contact with the Europeans, or their own internal affairs. Seeing that the European imperial powers are closing in and managing to occupy the nations in their surroundings, the Japanese were not willing to allow the same to happen to them. The country was unified, had very strong nationalistic core, and quickly started to cut down and move away the Europeans. The Christians were persecuted, while the European ships and merchants were expelled and not allowed to come to Japan.
Japan continued with its measures, and it started to rapidly industrialize.
The industrialization of the country resulting in more finances, large amount of which went for modernization and enlarging the army.
Japan became a very powerful country and let everyone know that it is not a good idea to try and engage into a conflict with it.
Instead of being occupied as the surrounding nations, Japan became an imperial power, gradually starting to conquer territories in East and Southeast Asia.
