A critical history of the events leading up to World War I and of the events of the first month of the war. It is centered on the first month of World War I. After introductory chapters, Tuchman describes in great detail the opening events of the conflict. Its focus then becomes a military history of the contestants, chiefly the great powers.

The Guns of August thus provides a narrative of the earliest stages of World War I, from the decisions to go to war, up until the start of the Franco-British offensive that stopped the German advance into France. The result was four years of trench warfare. In the course of her narrative Tuchman includes discussion of the plans, strategies, world events, and international sentiments before and during the war.