The social trauma caused by unprecedented rates of casualties manifested itself in different ways, which have been the subject of subsequent historical debate. Some people were revolted by nationalism and its results, and so they began to work towards a more internationalist world, supporting organisations such as the League of Nations.Pacifism became increasingly popular. Others had the opposite reaction, feeling that only strength and military could be relied upon in a chaotic and inhumane world. Anti-modernist views were an outgrowth of the many changes taking place in society.
The experiences of the war led to a collective trauma shared by many from all participating countries. The optimism of la belle époque was destroyed and those who fought in the war were referred to as the Lost Generation. For years afterwards, people mourned the dead, the missing, and the many disabled. Many soldiers returned with severe trauma, suffering from shell shock (also called neurasthenia, now called posttraumatic stress disorder). Many more returned home with few after-effects; however, their silence about the war contributed to the conflict's growing mythological status. In the United Kingdom, mass-mobilisation, large casualty rates and the collapse of the Edwardian eramade a strong impression on society. Though many participants did not share in the experiences of combat or spend any significant time at the front, or had positive memories of their service, the images of suffering and trauma became the widely shared perception. Such historians as Dan Todman, Paul Fussell and Samuel Heyns have all published works since the 1990s arguing that these common perceptions of the war are factually incorrect.