Answer:
It started with the "Black Ships" of 1854, when the USA forcibly opened up Japan for trade and westernization.
Explanation:
On the 1st of March 1854, Commodore Matthew Perry opened up Japan for trade by showing them his armada of steel ships which were superior to anything the Japanese had. At the time, the emperor had no real power, it was the Shogun who ruled the country. However, as the country westernized (becoming more like the western countries), Japan eventually had a government with different parties instead.
Ever since 1854, a feeling of nationalism had been growing since the Japanese were forced out of their old ways.
Also because westernization included colonialism, expansionism, capitalism, and nationalism
Nationalism in Japan in the 19th century (1800's) was not a big problem until the 20th century. It was then that the fear of communism created more nationalistic feelings, as well as that certain movements wanted Japan to rule East Asia. This eventually led to the unintentional invasion of China by the Kwantung army that the government had lost control of, which led to the Sino-Japanese war.
