I’m not 100% convinced, but the 20Committee makes a good case.
From Scott Anderson’s Lawrence in Arabia, p 69:
One reason Europe’s imperial powers missed the warning signs [about how catastrophic World War I would be] was that these new instruments of war had previously been employed almost exclusively against those who didn’t have them – specifically, those non-Europeans who attempted to resist their imperial reach. In such situations, the new weapons had allowed for a lopsided slaughter not seen since the Spanish conquest of the Americas, and more than any other single factor had accounted for the dramatic expansion of Europe’s colonial empires into Asia and Africa in the latter part of the nineteenth century.
It is perversely appropriate, then, that among the few people who did appreciate this new face of war and the problems it would pose was the man who had officiated over more of these one-sided battlefield slaughters than probably anyone else alive: Lord Kitchener. At the battle of Omdurman in the Sudan in 1898, Kitchener had trained his Maxim machine guns on horsemen charging with spears; at a cost of forty-seven British army dead, he had killed ten thousand of the enemy in a single morning. But what would happen when the other side had Maxims too? Kitchener had a pretty good idea. At that cabinet meeting on August 7 , where some other ministers imagined a conflict lasting months or even weeks, the newly appointed war secretary predicted years. “It will not end,” he told his colleagues, “until we have plumbed our manpower to the last million.”
As the ferocious battle wound down and enemy troops surrendered or retreated a wounded German soldier limped out of the maelstrom and into Private Tandey’s line of fire, the battle weary man never raised his rifle and just stared at Tandey resigned to the inevitable. “I took aim but couldn’t shoot a wounded man,” said Tandey, “so I let him go.” 
The young German soldier nodded in thanks and the two men took diverging paths, that day and in history. Hitler retreated with the remnants of German troops and ended up in Germany, where he languished in the humiliation of defeat at wars end.
Some things seem like a good idea at the time…