The German Empire consisted of 27 constituent territories, with most being ruled by royal families. This included four kingdoms, six grand duchies, six duchies (five after 1876), seven principalities, three free Hanseatic cities, and one imperial territory. Although the Kingdom of Prussia contained most of the Empire's population and territory, it played a lesser role. As Dwyer (2005) points out, Prussia's "political and cultural influence had diminished considerably" by the 1890s.
After 1850, the states of Germany had rapidly become industrialized, with particular strengths in coal, iron (and later steel), chemicals, and railways. In 1871 it had a population of 41 million people, and by 1913 this had increased to 68 million. A heavily rural collection of states in 1815, the united Germany became predominantly urban. During its 47 years of existence, the German Empire operated as an industrial, technological, and scientific giant, gaining more Nobel Prizes in science than Britain, France, Russia, and the United States combined.
Germany became a great power, boasting a rapidly growing rail network, the world's strongest army, and a fast-growing industrial base. In less than a decade, its navy became second only to Britain's Royal Navy. When the great crisis of 1914 arrived, the German Empire had only one ally – Austria-Hungary. They were later joined by the Ottoman Empire and Bulgaria to form the Central Powers or Quadruple Alliance.
In the First World War, German plans to capture Paris quickly in autumn 1914 failed, and the war on the Western Front became a stalemate. The Allied naval blockade caused shortages of food. Germany was repeatedly forced to send troops to bolster Austria and Turkey on other fronts. However, Germany had great success on the Eastern Front; it occupied large Eastern territories following the Treaty of Brest-Litovsk. German declaration of unrestricted submarine warfare in early 1917 was designed to strangle the British; it failed, because of the use of a trans-Atlantic convoy system. But the declaration—along with the Zimmermann Telegram—did bring the United States into the war. Meanwhile, German civilians and soldiers had become war-weary and radicalised by the Russian Revolution.
The high command under Paul von Hindenburg and Erich Ludendorff increasingly controlled the country, as they gambled on one last offensive in spring 1918 before the Americans could arrive in force, using large numbers of troops and artillery withdrawn from the Eastern Front. This failed, and by October the armies were in retreat, the Austro-Hungarian Empire and the Ottoman Empire had collapsed, and the German people had lost faith in their political system. The Empire collapsed in the November 1918 Revolution as the Emperor and all the ruling monarchs abdicated, and a republic took over.