LONDON — Seconds before an armistice formally ended World War I on Nov. 11, 1918, Pvt. Henry Nicholas Gunther, an American soldier from Baltimore, mounted a final, one-man charge against a German machine-gun nest in northeastern France.

The German gunners, The Baltimore Sun reported many years later, had tried to wave him away, but he ran on, only to perish in a burst of heavy automatic fire — the last soldier of any nationality to die in the conflict — at 10.59 a.m. local time. One minute later, under the terms of an armistice signed about six hours earlier, the so-called Great War, the “war to end all wars,” was over, and the world was an altered place.

The casualties since the conflict’s first engagements in 1914 ran into many millions, both military and civilian. The very nature of warfare had changed irrevocably. Empires crumbled, new nations arose and the world’s maps were redrawn in ways that reverberate mightily a century later. With men away at the front lines, women assumed roles in the work force back home that hastened their emancipation and changed social ways forever.