What’s the most important reason that the First World War was a total war?

What’s the most important reason that the First World War was a total war? (Lead with a common denominator argument and draw on examples from the film, the lecture, and the book excerpt from All Quiet on the Western Front).

500 WORDS FOR THIS ANSWER.

Refer to the movie All Quiet on the Western Front as well. Talk about PTSD if you can.