I think Les is right there was lots of things happening prior to war breaking out. Initially Britain looked to an alliance with Germany but was basically rebuffed and it seems the Kaiser by then saw Britain as the main competitor rather than friend. So Britian cosied up to France instead and later Russia. Germany was bolshie and looking out for its own interests but so was Britain and France who were making secret treaties involving Morocco etc which they had no legal right to do. According to H.L.Peacock in his "A History Of Modern Europe" the events after Sarajevo and the break out of hostilities between Austria and Serbia went like this chronoligacally. July 28th Austria declares war on Serbia; Russia immediately mobilises in support of Serbia; Germany immediately demands that Russia demobilises and that France assures neutrality; Russia refuses and Germany declares war on Russia on 1st August then on France on 3rd August; on 4th August Germany strikes at France through neutral Belgium believing that Britain wouldn't go to war over a piece of paper.

In the summing up he says German aggresiveness was greatly to blame but that it would be wrong to think that all aggresiveness was centred on Germany. There were those in Britain who favoured a war with Germany before that country became too strong; there were those in France who wanted revenge for the war of the 1870s; and pan-Slavism was as much a problem as pan-Germanism.