This book aims to offer a brief and comprehensive overview of all the key aspects of the war, as well as a small chapter on the Greek aspect, attempting to summarize in a few pages the basic knowledge that has been accumulated and codified for each of these much-discussed parameters. At the same time, it leverages the great momentum from the centenary events to address the questions and new challenges of research on the subject at an international level. A book that is addressed both to the general reader and to the historian scientist, as it serves as a guide for approaching and understanding a pivotal event in world history, consciously adopting a simple and understandable narrative.