There is one major character in early XX century history, that often goes ignored. Erich von Ludendorff.
This guy served under Paul von Hindenburg and when he replace Falkenhayn, Erich von Ludendorff became quartermaster general for the whole of Germany.
He transformed the German society into a war economy, a dictatorship where everything was made for the German Heer. For a while, he probaly had more power than Hindenburg or even the Kaiser.
Not only that, but when Germany defeated Russia and signed the treaty of Brest-Litovsk, Ludendorff made plans to map the ethnic Germans and non-Germans in the newly occupied territories, with the plan of expanding Germany for Germans.
If this sounds like the Lebensraum that Hitler later wrote about, it's probably because it is.
After the war ended, he became instrumental in spreading the myth that Germany lost because it was backstabbed.
When Hitler was on the rise in German politics, Ludendorff was right next to him. Including during the Bavarian putsch. Hitler and other Nazi were arrested, but Ludendorff being a high ranking member of the army, was spared.
Ludendorff was very influential with Hitler and his militaristic ideas, very likely influencing a good chunk of Mein Kampf.
But it's not just with Nazi Germany that Ludendorff had a strong influence. Even before WW1 he was a prominent military writer, who advocated that the civil society should be subservient to the army.
That civilians should make goods so that the army could have the power and strength to fight and conquer it's neighbours.
This was very influential in the view that many military officers had in Japan during the 20's and 30's.
We usually call it Imperial Japan, but during WW1, most of he power was held by the military. Namely the navy and the army, who in turn hated each other.
This is why, even today, Japan's society have a very strong suspicion regarding their own military. They already had a military dictatorship, and it went very bad for the civilians.