A handful of belligerent political leaders, primarily in Berlin, but also in Vienna, exploited the murder of the heir to the Austro-Hungarian throne Archduke Franz Ferdinand to pursue their long-held belief in Germany’s need for a world policy ‘Welpolitik’, even the right to world power ‘Weltmachtstellung’. Their machinations, deviousness, obfuscations and at times ineptitude and delusions, led Britain’s leaders, reluctantly, in August 1914, once all efforts at mediation had failed, and enough of Britain’s divided Cabinet could unite after Germany’s invasion of Belgium, to enter a state of war when Germany failed to respond to Britain’s 4th August ultimatum.
That's Nothing Compared to Passchendaele 