Wars with China and Russia

Japanese intellectuals of the late-Meiji period espoused the concept of a "line of advantage," an idea that would help to justify Japanese foreign policy at the turn of the century. According to this principle, embodied in the slogan fukoku ky?hei, Japan would be vulnerable to aggressive Western imperialism unless it extended a line of advantage beyond its borders which would help to repel foreign incursions and strengthen the Japanese economy. Emphasis was especially placed on Japan's "preeminent interests" in the Korean Peninsula, once famously described as a "dagger pointed at the heart of Japan." It was tensions over Korea and Manchuria, respectively, that led Japan to become involved in the first Sino-Japanese War with China in 1894-1895 and the Russo-Japanese War with Russia in 1904-1905.
The war with China made Japan the world's first non-Western modern imperial power, and the one with Russia proved that a Western power could be defeated by a non-Western State, thus questioning the idea of European superiority prevailing in most countries dominated by Western powers. All sorts of political movements in different territories around the world that were oppossing European occupation or intervention, started to use Japanese victory in their propaganda and speaches. The global struggle against colonialism and imperialism benefited from Japan's experience.
For Japan and for the moment, it established the country's dominant interest in Korea, while giving it the Pescadores Islands, Formosa (now Taiwan), and the Liaodong Peninsula in Manchuria, which was eventually retroceded in the "humiliating" Triple Intervention. Over the next decade, Japan would flaunt its growing prowess, including a very significant contribution to the Eight-Nation Alliance, formed to quell China's Boxer Rebellion. Many Japanese, however, believed their new empire was still regarded as inferior by the Western powers, and they sought a means of cementing their international standing. This set the climate for growing tensions with Russia, who would continually intrude into Japan's "line of advantage" during this time.

World War I

In a manner perhaps reminiscent of its participation in quelling the Boxer Rebellion at the turn of the century, Japan entered World War I and declared war on the Central Powers. Because Japan's role in World War I was limited largely to attacking German colonial outposts in East Asia, it permitted Japan to expand its influence in Asia and its territorial holdings in the Pacific. Acting virtually independently of the civil government, the Japanese navy seized Germany's Micronesian colonies. It also attacked German possessions in Shandong. The post-war era brought Japan unprecedented prosperity. Japan went to the peace conference at Versailles in 1919 as one of the great military and industrial powers of the world and received official recognition as one of the "Big Five" of the new international order. It joined the League of Nations and received a mandate over Pacific islands north of the Equator formerly held by Germany. Japan was also involved in the post-war Allied intervention in Russia, occupying Russian (Outer) Manchuria and also north Sakhalin (with its rich oil reserves). It was the last Allied power to withdraw from the interventions against Soviet Russia (doing so in 1925).
During the 1920s, Japan progressed toward a democratic system of government in a movement known as 'Taisho Democracy'. However, parliamentary government was not rooted deeply enough to withstand the economic and political pressures of the late 1920s and 1930s, during which military leaders became increasingly influential. These shifts in power were made possible by the ambiguity and imprecision of the Meiji Constitution, particularly its measure that the legislative body was answerable to the Emperor and not the people, and the 2.26 Incident. Party politics came under increasing fire because it was believed they were divisive to the nation and promoted self-interest where unity was needed. As a result, the major parties voted to dissolve themselves and were absorbed into a single party, the Imperial Rule Assistance Association (IRAA), which also absorbed many prefectural organizations such as women's clubs and neighborhood associations. However, this umbrella organization did not have a cohesive political agenda and factional in-fighting persisted throughout its existence, meaning Japan did not devolve into a totalitarian state. The IRAA has been likened to a sponge, in that it can soak everything up, but there is little one could do with it afterwards. Its creation was precipitated by a series of domestic crises, including the advent of the worldwide economic depression in the 1930s and the actions of extremists such as the members of the Cherry Blossom Society, who enacted the 5.15 Incident.