How did World War I affect the lost generation?

World War I exerted a profound impact across the first half of the Twentieth Century. The thing to keep in mind was the sheer scale of death and suffering, which far exceeded any military conflict which preceded it. This level of death was further exacerbated by the outbreak of the Spanish Flu epidemic, which may have killed an estimated 50 million people on its own. In addition, we can discuss the experience of trench warfare and the introduction of chemical weapons and mustard gas to the battlefield; it is easy to discern how there might be severe psychological scars moving forward.
To examine the implications of this moment, we would need to think about the trends of the 1920s and 1930s with the experience of World War I in mind, and consider whether or not we can see its influence at play. Politically, we can talk about political treaties, such as the Kellogg-Briand Pact, and consider what this suggests about the general mood of these countries. Additionally there is the culture of the Roaring Twenties: how would we describe the Jazz Age, what are its characteristics, and can we draw a connection between those characteristics and the trauma of the First World War? Finally, we can think about the rise of Fascism and Totalitarianism in countries such as Germany and Italy, and consider how this impacts the analysis.