There were, of course, many changes in Japanese politics over that time. Let us look at two major changes.
First, there was the move towards more party politics beginning around 1905 and culminating in the Taisho Political Crisis of 1912. During this period, parties became more organized and gradually gained power at the expense, in particular, of the oligarchs (later called genro) who surrounded the Emperor. From this point, parties generally grew in power.
But this growth of power ended and started to retreat in the late 1920s. From there on, the power of the military increased. Japan became much more aggressive and militaristic in its foreign policies. The military came to have and to exert more influence in the government. This change helped to cause the invasion of China and eventually World War II.