Just continuing the Teribus point, German military thinking was held in the straightjacket of the "Schlieffen Plan" - as France and Russia were bound my a military alliance, Germany would be facing a war on two fronts - Russia had mobilised in support of its ally Serbia - it was generally thought that the Russian army would take six weeks to get ready owing to distances etc. The Germans had defeated the French in five weeks in the Franco-Prussian War and it was reckoned that if they could do the same again, they would then be free to use all their forces against Russia. The Russian mobilisation meant that this would no longer be possible, and caused the German High Command to go into panic mode as there was no "plan B" - Schlieffen himself had died some years earlier. There was also the miscalculation in thinking the British would not stick by a treaty with Belgium going back to 1839.