To what extent was Germany responsible for the outbreak of WWI?

There is much debate about the degree of responsibility that should be given to Germany for the outbreak of war. One could argue that the outbreak of war was entirely Germany’s fault due to their aggression with the other Great Powers of Europe and the very presence of the Schlieffen Plan. One could also argue that Germany was merely protecting herself against aggression and the idea of encirclement. Or was it a misfired attempt at strengthening relationships with the Entente powers? Either way one can deduce that Germany had a significant role in the outbreak for war, but should not necessarily be held fully accountable.

Aggression already existed between the Entente
Germany offered Austria-Hungary unconditional support if they were to move and attack Serbia. Slav populated Austria-Hungary was worried about the upheaval in the Balkans, the ousting of Turkish influence planted the seed of fear that the empire would eventually dissolve if Serbia, the leading force in the Balkan movement, were to make a single Slavic state. Austria aimed to suppress this movement and Germany, believing that if Austria were to war with Serbia it would remain a localised war. Bethmann Holweg, the German chancellor of the time believed that the defeat of Serbia would weaken ties between Russia and Serbia, (assuming Russia would not intervene due to financial and technological lapses at the time), then through Austrian success, Germany could improve its relationship with the nations of the Triple Entente without ever engaging in war, as the so-called ‘Blank Cheque’ never stated that Germany would go to war with Austria, but merely would support their movements and this meant that Germany relatively remained neutral within the Great Powers.
The ‘blank cheque’ was intended so that Germany could remain neutral with both Austria and the Entente powers but was based on a gamble of other nation’s actions, Germany at the