Captain Horatio Hornblower R.N. (released in the U.S. without the 'R.N.') is a 1951 naval adventure film. It was directed by Raoul Walsh and stars Gregory Peck, Virginia Mayo, Robert Beatty and Terence Morgan.
It was based upon three of C. S. Forester's Horatio Hornblower novels, The Happy Return (Beat to Quarters in the United States), A Ship of the Line and Flying Colours. Forester is credited with the adaptation; as a result, the film is faithful to his novels and features an occasionally introspective tone unusual for an old-fashioned swashbuckler.
In 1807, during the Napoleonic Wars, English Royal Navy Captain Horatio Hornblower (Gregory Peck) commands the 36-gun frigate HMS Lydia on a lengthy secret mission to Central America. He is to provide arms and support to a megalomaniac calling himself "El Supremo" or "The Almighty" (Alec Mango) in his rebellion against Spain, an ally of Britain's enemy France. As Hornblower observes to First Lieutenant Bush (Robert Beatty), "War breeds strange allies."
Upon his arrival, Hornblower is told that a larger, much more powerful Spanish warship, the 60-gun Natividad, has been sighted. When it anchors nearby, Hornblower and his crew board and capture it in a surprise nighttime attack. He then reluctantly hands the ship over to El Supremo to appease the madman, and they go their separate ways.
Later, he encounters a small Spanish vessel and learns that Spain has switched sides, so the Lydia will have to attack the Natividad again. Two passengers transfer to the Lydia (over Hornblower's objections): Lady Barbara Wellesley (Virginia Mayo) and her maid, fleeing a yellow fever epidemic. As Lady Barbara is the (fictitious) sister of the Duke of Wellington (an anachronism, as the title was created in 1814 and he would have been Sir Arthur Wellesley at this time), Hornblower is in no position to refuse her request for passage to England.
Using masterful tactics, Hornblower sinks the Natividad, and when the ship's surgeon is killed in the battle, Lady Barbara insists on helping by nursing the wounded. When she later falls gravely ill, Hornblower nurses her back to health. On the voyage back to England, they fall in love. However, when she makes advances (although she is engaged), Hornblower informs her he is married.
After arriving home, Hornblower learns that his wife has died in childbirth, leaving him an infant son. He is given command of the Sutherland, a powerful ship of the line captured from the French, and is assigned to a squadron commanded by Rear Admiral Leighton (Denis O'Dea), Lady Barbara's new husband. The squadron's mission is to help enforce the British blockade against Napoleonic France.
At a conference on Leighton's flagship, Hornblower learns that four French ships of the line have broken the blockade. Leighton assumes they will make for the Mediterranean, but Hornblower suggests that they mean to support Napoleon's campaign on the Iberian Peninsula.
Leighton decides to cover both possibilities by detaching one ship to patrol the French coast. When he learns that Hornblower's Sutherland is best suited for this task, having the shallowest draught, he becomes suspicious that Hornblower is after glory and prize money. Leighton therefore expressly forbids Hornblower from taking any independent action if he sights the French.
Hornblower's French-built ship is subsequently mistaken for a friendly vessel by a small French brig, which flies the enemy's recognition signal for the day. After capturing the vessel, Hornblower learns from interrogating its captain that he was transporting army supplies to the four warships for use in Spain. Rather than return to the squadron, Hornblower sends the brig back with a prize crew and the news.
He enters the enemy harbour where the French ships are anchored and guarded by a well-armed fort. By flying a French flag and the recognition signal and taking advantage of the appearance of his ship's French design, Hornblower fools the garrison into believing that the Sutherland is friendly. His gun crews dismast all four enemy ships before French cannon fire forces the British to abandon the Sutherland. Hornblower scuttles his ship in the channel, bottling up the French ships.
As the rest of the British squadron arrives to complete the job, Hornblower and Bush, accompanied by seaman Quist (James Robertson Justice), are taken by carriage to Paris to be tried for piracy. However, they manage to escape en route and make their way to the port of Nantes. Disguised as Dutch officers, they board The Witch of Endor, a captured British ship. They overpower the skeleton crew, free a working party of British prisoners of war to man her, and sail away to freedom.
Hornblower is hailed as a national hero, and learns that Leighton was killed in the battle. Hornblower returns home to visit his young son, and finds Lady Barbara there. The two embrace.