Kaiser Wilhelm II (27 January 1859 - 4 June 1941) was the last German Emperor and King of Prussia, reigning from 1888 to 1918. He was the eldest grandchild of the Queen Victoria of Britain and related to many monarchs and princes of Europe.
Upon his ascent, he dismissed the Chancellor, Otto von Bismarck, in 1890 and launched Germany on a bellicose "New Course", seeking at once to assert more absolute control over his own government while conducting foreign relations with the goal of making Germany an important country in global affairs. However, this new course systematically alienated most of Germany's neighbors, as Wilhelm tended to support belligerence and militarism over diplomacy.
Conversely, certain aspects of his domestic policy were quite progressive for the time, as Wilhelm pushed for, and received, legislation that protected the German workers. He also supported science, the arts, education, and public welfare. However, Wilhelm also maintained a healthy antisemitism, often lamenting what he saw as the undue influence the Jews exerted over Germany.
When Franz Ferdinand of Austria was assassinated in Sarajevo in 1914, Wilhelm promised to support Austria-Hungary in any action it might take against Serbia. When Russia went to war with Austria-Hungary, Wilhelm II honored the Central Powers alliance, bringing his country into what became the First World War. By 1918, Germany had been defeated, and Wilhelm was overthrown and the German monarchy was abolished. He fled Germany and spent the rest of his life in the Netherlands until his death on 4 June 1941.
Wilhelm II led Germany through the brief war in 1914, in which France, Britain, and Russia were defeated. He led his country to victory against France and Britain again in the late 1930s, making Germany the supreme power in Europe. Upon his death in 1941, he was succeeded as Kaiser by his son Wilhelm III.
The last statement is speculative, based on the fact that he died then in OTL.
Wilhelm died in June 1941 and was succeeded by his son Wilhelm III. The Entente took advantage of his death to launch a coordinated attack on Germany, beginning the Second Great War.
In the earlier part of the 20th century, it was common for U.S. men - especially members of the armed forces - to sport what was affectionately referred to as "a Kaiser Bill Moustache". This was linked to the Remembrance ideology and the wish of Americans to emulate Germany and achieve victory over the hated Confederates. This style faded away after the end of the Great War.