As German imperialist zeal flourished, it was inevitable that the young power would come into conflict with the older, more established colonial empires. An increasing series of frictions with Britain, France and Belgium over clashing interests finally led to the outbreak of a major conflagration in 1914.
The jumble of events, entangled alliances, trip-wire strategic planning and plain bad luck that dragged the major combatants into this conflagration are too complicated to go into here. Enough to say that Germany, allied with the Austrian and Ottoman empires, moved first and quickly, though it is unfair to pin sole blame on Germany, as some would.
Although the powerful, dynamic young country scored a number of impressive early victories, they soon found themselves bogged down in a long, dirty, frustrating fight with their main opponents - Britain , France, and the Russian Empire. The extent and immeasurable human costs of this conflict led it to be called the Great War, though 20 years later it had to be renamed the First World War.
The U.S. entry into the war in early 1917 finally tipped the balance against Germany and its allies. By the end of 1918, it had become increasingly clear that Germany was heading for a stinging defeat. In the final months of 1918, Germany's main allies were not only falling, they were reeling, and Germany - which had staked the most in this war - was soon forced to join in. In early November, the progressive forces in the Reichstag declared the first German republic, then forced the Kaiser and the middle-level kings to abdicate, and Germany surrendered unconditionally.