That's what got me too. I see these trenches, dug deep and filled with wooden constructions, backed by layers of rocks that were moved and placed there. All done, I imagine, mostly by hand and perhaps with the help of beasts of burden.
And then I think of the number of soldiers involved - I guess if each dug a hole and nailed some boards, such trenches could be built quickly. After all, man power scales not just by power, but by number of people as well.
(And then I start thinking about the logistics to feed all these soldiers, and my head starts to spin.)
I study WW2, and at the start you're unsettled by the number of casualties (in the realm of 70 million through 1945.)
But over time you also realize the entire industrial output of the Allies was used to defeat the Axis, and you become completely disgusted at the monumental waste.
Historians agree that the Axis never had a chance of winning in the longterm (aside from extreme luck), and WW2 was a result of US isolationism. Had the US promised to send 2 million troops to Europe as in WW1, Germany would not have bothered with most of their adventures.
We've had relative peace since 1945 thanks to US military investment, but one passive speech from the Whitehouse can undermine that deterrent, as Jimmy Carter did before.
The US didn't have 2M active duty troops available to send to Europe in 1939. We were still in the Great Depression. Even if there had been political will to oppose the Axis Powers at that time, the funding and materiel simply didn't exist.
