The unified German Empire, proclaimed on January 18, 1871, lasted until 1918, and was formed after 3 successive wars with Denmark, Austria, and France in the late 1860's to early 1870's. These wars, won by the Prussian military prowess, were to incorporate ethnically disputed territory into Germany. However, the Empire incorporated many different ethnic groups, and this became a major problem -- about one third of the new inhabitants of the Empire were Roman Catholic, and owed allegiance to the Pope along with the Emperor. The German leaders felt that allegiance to the Emperor was supreme, and a series of Anti-Catholic acts followed. Who controlled education, church or state, became a major conflict. Finally, bishops and priests were imprisoned or expelled. Additionally, as Germany became a major industrial power during this era, the working class pushed a socialist agenda that conflicted with the interest of the landed gentry. Finally, the legislative branch of the German government, the Reichstag, could not initiate legislation! Although the government modernized from a bit from an absolute monarchy, the crippling of the legislature meant that the elected representatives could not respond to the changing needs of the electorate.
Interestingly, Germany may have grown overconfident that its military could be quickly brought to bear to decide ethnic and territory disputes. Although such tactics worked in the latter 19th century to help establish the Empire, in the 20th century they failed absymally and led the Empire to destruction, when she attempted to aid Austria during crisis in the Balkans in August, 1914.