The 100th anniversary of the outbreak of World War 1 could be viewed as a tempting opportunity to acknowledge the origins of military psychiatry and the start of a journey from psychological ignorance to enlightenment. However, the psychiatric legacy of the war is ambiguous. During World War 1, a new disorder (shellshock) and a new treatment (forward psychiatry) were introduced, but the former should not be thought of as the first recognition of what is now called post-traumatic stress disorder and the latter did not offer the solution to the management of psychiatric casualties, as was subsequently claimed. For this Series paper, we researched contemporary publications, classified military reports, and casualty returns to reassess the conventional narrative about the effect of shellshock on psychiatric practice. We conclude that the expression of distress by soldiers was culturally mediated and that patients with postcombat syndromes presented with symptom clusters and causal interpretations that engaged the attention of doctors but also resonated with popular health concerns. Likewise, claims for the efficacy of forward psychiatry were inflated. The vigorous debates that arose in response to controversy about the nature of psychiatric disorders and the discussions about how these disorders should be managed remain relevant to the trauma experienced by military personnel who have served in Iraq and Afghanistan. The psychiatric history of World War 1 should be thought of as an opportunity for commemoration and in terms of its contemporary relevance—not as an opportunity for self-congratulation.