German responsibility was not limited to the imprudence of the Kaiser and his chancellor, however. It also involved generals who were looking for war against Russia (and its ally, France). Since 1908 the Kaiser and his entourage had been dominated by the military, among whom social Darwinism was a prevailing orthodoxy. For the German general staff and its chief, Helmuth von Moltke (the younger), international relations were about the struggle for survival — and so the dominance — of ethnic nations, and war was the natural way of deciding it. At the war council of December 8, 1912 Moltke pressed the view that a European war was inevitable and that, as far as Germany was concerned, the sooner it happened the better. His advocacy of preventive war prevailed. Twenty months later, when both the Kaiser and Bethmann-Hollweg got cold feet over the prospect of a continental war and called on Austro-Hungary to halt its invasion and seek terms with Serbia, Moltke by-passed the chancellor and urged the chief of the Austrian general staff to mobilise against Russia, promising him that Germany would follow suit. Later that evening Moltke persuaded Bethmann-Hollweg to decide on general mobilisation, regardless of Russian equivocation. Two days later Germany declared war on Russia.

It was the German government, and especially its military leadership, that first risked and then caused continental war in August 1914. Why did they do it? Because they took it for granted that war is the natural way of deciding the balance of international power; because they foresaw that the longer the next war was delayed, the longer the odds against Germany's victory would be; because they were determined at least to maintain Germany's ability to back its wishes by credible military force and therefore its status as a Great Power; and because (to quote Stevenson) the memory of the 1870 Franco-Prussian War "still nurtured through annual commemorations and the cult of Bismarck, had addicted the German leaders to sabre-rattling and to military gambles, which had paid off before and might do so again." Germany's leaders were not sleepwalkers, but fully conscious moral agents, making decisions according to their best lights in a volatile situation of limited visibility. Error was forgivable. Not forgivable, however, was their subscription to the creed of Darwinist realpolitik, which robbed their political and military calculations of any moral bottom line.

It is natural for a nation not to want to see its power to realise its intentions in the world diminished. But if social Darwinism thinks it natural for a nation to launch a preventive war simply to forestall the loss of military and diplomatic dominance, just war reasoning does not think it right. Just cause must consist of an injury and Germany had suffered none. Nor was it about to: there is no evidence that Russia, France, or Britain intended to attack. On the contrary, Russia mobilised only after Berlin had already flirted with general war and then decided upon it. As for France, it had deliberately kept one step behind Germany in its military preparations so as to make its defensive posture unmistakable, and as late as August 1 France reaffirmed the order for its troops to stay ten kilometres back from the Franco-Belgian border. Notwithstanding this, Germany declared war on France on August 3 on the false pretext that French troops had crossed the border and French aircraft had bombed Nuremberg. 

In Britain a majority of the Cabinet was against entering the fray until August 2. The Entente Cordiale only obliged the British to consult with the French in case of a threat to European peace, and not automatically to activate their joint military contingency plans. What eventually decided the Cabinet in favour of war on August 4 was Germany's violation of Belgian neutrality. In British minds "Belgium" conjured up a variety of altruistic just causes: honouring a treaty to guarantee Belgian independence, punishing a violator of the treaty, and defending the rights of small nations. It also involved British national security, however, since the Belgian coast faced London and the Thames estuary, and it had therefore long been British policy to keep that coastline free from hostile control to prevent invasion and preserve command of the sea. It is true that, in rising to Belgium's defence, the British also sought to forestall a German domination of Europe that they found menacing. Nevertheless, Britain did not initiate a war to maintain a favourable balance of power, nor would it have intervened to maintain it without the invasion of Belgium. 

Germany had suffered no injury, nor was it under any immediate or emergent threat of suffering one. Unprovoked, it launched a European war to assert and establish its own military and diplomatic dominance. In response, Britain went to war primarily to maintain international order by upholding the treaty guaranteeing Belgian independence and by resisting its violator, and to fend off a serious threat to its own national security. In so doing it sought, secondarily, to prevent the domination of Europe by a power that had shown itself willing to unleash war on its studiously unprovocative neighbours. 

But given what we now know of the terrible cost of resistance, it is reasonable to wonder whether it would not have been proportionate — in the sense of "prudent" — for Belgium, France, Russia and Britain to suffer domination by Germany instead. How bad would that really have been?