This slim novel by C.S. Forester follows the progress of an 18-pounder siege cannon back and forth across northern Spain as spanish rebels attempt to use it to strike a blow against Napoleon, who has recently annulled his alliance with Spain, invaded, and put his brother on the throne. Intruigingly written, the book's main character is the gun itself - the men who command it taking second place, and frequently dying at each other's hands as the gun changes hands.

It is a careful and thoughtful account of a small rebel action, covering the details of the battles the gun is involved in and the human cost of the war equally. Forester's only real sins in the book are his usual immense pride in the English navy (although he details its shortcomings at length in the Hornblower books), and a somewhat jaundiced view of Spanish soldiers.

All in all, it is an enjoyable and illuminating read, although if you like happy endings you should be wary, since it has a similar bleak and realistic ending to many of the Hornblower stories.