The book was first published in 1933 and has as its background the brutal war of liberation of Spanish and Portuguese forces (regular and partisans) and their British allies against the occupying armies of Napoleonic France.

[1] As the story begins, the titular huge bronze cannon is abandoned by the remnants of a regular Spanish army retreating after their defeat in the Battle of Espinosa.

The local people wish to employ it in their resistance against the French, but are eventually forced to hide it away beneath a pile of stone to prevent its capture.

Years later, a group of guerrilleros learn of its location and conscript the locals to outfit it with carriage and train.

The exploits of the Spanish irregulars under Jorge eventually lead to the diversion of a large body of elite French troops from reinforcing the army opposing the Peninsular allies under the Duke of Wellington.