The Marxist idea in World War One is that there would be Europe wide a class revolution to end World War One. The history of existing society for all of human history has not actually been about class conflict. In fact, virtually no conflicts in the history of humanity have been fought purely over class. And if only we could redistribute, if only we can subsidize, we could do all of that and we could create solidarity again. All we would have to do is change the economic systems by which we live. But it's not true. Marx was wrong,. but his idea continues to be the motivating factor in nearly all thinking politically still.