The answer to your question is German Emperor Wilhelm II (also known as William II). World War I began in 1914 with the assassination of Archduke Ferdinand and it was Wilhelm II that was the emperor of Germany at this time. Wilhelm II ruled Germany from 1859-1941. He was a grandson of Queen Victoria known specifically for not only ruling Germany but also for ruling the kingdom of Prussia at the time. (He is further known as "King of Prussia.")
In regards to World War I, Wilhelm II is known as one of the fire-starters. Why? In the late 1800s he fired the chancellor Otto Von Bismark and sent Germany into a more belligerent state of history. It seems that Wilhelm II simply was not patient enough to endure Bismark's more careful dealings in foreign policy. Specifically, Wilhelm II wanted "vigorous and rapid expansion" and wanted to connect Germany with Austria-Hungary, even in regards to the "crisis of 1914," which directly led to Archduke Ferdinand's assassination, World War I and the creation of the Central Powers.