During the
Peninsular War, Napoleon's armies overrun Spain. An enormous siege cannon, belonging to the Spanish army, is abandoned when it slows down the army's retreat. French cavalrymen are dispatched to find it. Britain, Spain's ally, sends a Royal Navy ordnance officer, Captain Anthony Trumbull, to find the huge cannon and see that it is handed over to British forces before it can be retrieved by the French. However, when Trumbull arrives at the Spanish headquarters, he finds that it has been evacuated and is now occupied by a guerrilla band led by the French-hating Miguel. Miguel shows Trumbull the abandoned cannon's location at the bottom of a steep ravine. He says he will only help move the huge gun if it is first used against the fortified walls of
Ávila, which Miguel is obsessed with capturing. During their association, the two men grow to dislike each other. One cause of their enmity is Miguel's mistress, Juana, who falls in love with Trumbull. Meanwhile, sadistic General Jouvet, the French commander of the French forces in Ávila, orders the execution of 10 Spanish hostages daily until information on the cannon's whereabouts is surrendered. The cannon has, in fact, been recovered and undergoes an arduous journey across Spain toward Ávila. The guerrilla band, whose ranks have swelled considerably, almost lose the cannon when General Jouvet deploys artillery at a mountain pass that they must use to get to Ávila. With help from the local populace, the band gets the cannon through, despite heavy losses, although it rolls down a long hillside and is damaged, becoming partially dismounted from its transport carriage. The cannon is moved and hidden inside a cathedral while it is repaired. Afterwards, it is disguised as an ornamental processional platform during a Catholic Holy Week religious procession in order to move it past the occupying French. French officers, however, are informed of the cannon's cathedral location, but by the time they arrive, it has been repaired and moved, leaving no trace that it was ever there. When the cannon finally arrives at the guerrillas' camp on the plains outside Ávila, Trumbull and Miguel prepare to attack the city. However, Ávila is defended by
strong walls, eighty cannon and a garrison of French troops. Trumbull explains to the assembled guerilla force that half their number will be killed by various types of French artillery shot and grouped rifle fire during their assault wave. Later, he tries to convince Juana not to participate in the battle, but, having come so far, the next day she goes with the men. Trumbull repeatedly fires the huge siege cannon, its large solid shot slowly demolishing one section of Ávila's high walls. Despite suffering heavy losses as they charge forward, the guerrillas pour through the city's breached wall and overwhelm the French forces. General Jouvet is killed, and the last French troops are overrun and killed in the town square. After the battle, Trumbull bids farewell to a dying Juana and then places Miguel's dead body at the foot of the statue of Ávila's
patron saint Saint Teresa. After securing the huge cannon for its long journey to England, Trumbull leaves Ávila with troubled memories of his adventures across Spain. ==Cast==