Max Hastings of course includes all the possible factors in Catastrophe, a highly readable popular history of the start of the war. And concludes that Germany was primarily responsible. And this is the conventional view; the condemnation of Germany at Versailles was just, if the reparations were not. The German novelist Alfred Döblin captures the views of ordinary Germans in 1918, and does more to explain the causes of Hitler's rise than a tonne of academic histories. Hastings I think has missed a trick. He covers German 'beastliness' in Belgium but fails to develop its consequences; likewise, Der Spiegel's German historians who theorize that Hitler learned the machinery of repression from the Soviets have missed a trick in looking east rather than west.
Sometimes it's the minutiae that give useful insight. The design of British tanks that uniquely always includes a small boiler to allow the crew to brew-up. And John Lodwick, SOE and a much neglected novelist, writes of his experiences as an on-off prisoner of the Germans and their camp layout that inevitably included in addition to barracks, latrines and canteen a pig-killing pit. The Heer in the second, as in the first, war was made up of men who could handle horses, were happy outdoors and who could slaughter and butcher pigs with unconcern.
If the British learned successful counter-terrorism techniques from Malaya, a small country far away, is it so extraordinary to suggest that Germany learned occupation from Belgium, the only western European country she occupied in the Great War? Were the lessons learned in Belgium applied later in France, Denmark, Norway, Greece and the rest? Army manuals are written by soldiers with relevant experience, not journalists. Blueprints for internment camp layout and administration must have come from Germans who had run them in Belgium, not journalists who had seen them in Russia. Plans for well-organised civilian round ups and internment were learned from the mass-round-ups of Belgians, not Kulaks.
I have a folio of lithographs drawn by a Belgian artist in 1918, after his release from the German concentration camps. Each time I look through them, I see the model for Hitler's Reich. Here's a sample.