Buchan covered World War I for TheTimes of London, as well as working for Britain’s War Propaganda Bureau. Collected here are his observations and analysis. The autumn of 1917 saw Germany in trouble and Russia’s downfall, which is where this fourth and last volume picks up. The last section of Buchan’s ambitious series is called “The Surrender,” and closes with a glance back at, and mindful analysis of, the Great War.