a very long novel with many short chapters (could be endlessly serialized in magazines before eventual book publication);
each chapter shows the protagonist in combat in a major war, starting in prehistory, passing through many historical periods and the present and into the future which also has many dissimilar periods, e.g., war on Earth in the twenty-fourth century is very different from war on Mars in the twenty-sixth century;
no up-front explanation of why this guy is alive in all these periods (think of John Carter, always a soldier, remembering no childhood);
some ambiguity as to whether he is killed at the end of some of the chapters, e.g., is he killed in an explosion or just concealed by smoke?;
maybe a future period of global peace when our protagonist does not seem to exist?;
a further future in which a Time Travel Institute plans to send a man to experience combat in many past periods;
if killed, he can be retrieved, resurrected and sent back.