The historical adventure was one of the most successful offshoots of the Romantic movement in literature of the late 19th and early 20th centuries. A number of writers were greatly inspired by pirate themes, none more so than Rafael Sabatini (1975-1950), whose novels of derring-do on the high seas and in the courts of Europe were quickly acquired as promising properties and given lavish treatment by several movie studios in the silent era.

Warner Brothers acquired the rights to Rafael Sabatini's 1915 novel The Sea Hawk in 1929 when the studio took control of First National Pictures, which had filmed a silent version of the novel in 1924. It told the tale of an English gentlemen, Sir Oliver Tressilian, who is accused of murder and shanghaied, thanks to the machinations of his evil half-brother. Captured by Spaniards at sea, Sir Oliver becomes a galley slave but escapes with the help of some Moors, who nickname him the Sea Hawk for his subsequent prominence among the Barbary Coast Corsairs. The buccaneer eventually clears his name and saves his ladylove from his brother's clutches.

When Errol Flynn became an overnight sensation in the hit swashbuckler Captain Blood (1935), based on another Sabatini novel, the studio immediately began looking for a suitable follow-up. Sabatini's Sea Hawk story seemed a natural choice.

Contract writer Delmer Daves was assigned the task of updating the story. He completed his screenplay in 1936, but by that point, the studio already had several other projects lined up for Flynn, all adventure pictures.

By 1939, with a string of successful Errol Flynn hits in release, the studio finally decided to go ahead with a production of The Sea Hawk, but instead of using Sabatini's original story, they turned to an original story they had bought a short time before from Seton I. Miller, one of the writers credited with the script for Flynn's box office smash The Adventures of Robin Hood (1938). Miller's "Beggars of the Sea" centered on a character loosely based on real-life Elizabethan-era privateer and seafarer Sir Francis Drake and contained many of the elements that made so many of Flynn's movies box office magic.

Executive Producer Hal B. Wallis, head of production at Warners, didn't like the script Miller wrote from his treatment and ordered it to be revised by Hollywood newcomer Howard Koch, who had recently made an impact as the original adapter of Orson Welles's notorious 1938 radio broadcast of H.G. Wells's War of the Worlds. Koch was also assigned to do some (uncredited) work on the Flynn Western Virginia City (1940). An ardent anti-fascist, Koch was working on his draft of The Sea Hawk as war broke out in Europe, so he used the historical basis of England's conflict with Spain under the reign of Elizabeth I to parallel the country's struggle against Hitler and Nazi Germany, a connection particularly obvious in a scene in which Spain's monarch looks at a map of the world, relating his plans to conquer all of it and raging against England as "a puny, rock-bound island" standing in his way.

The blatant political analogy was eagerly approved by Flynn, director Curtiz, and producer Henry Blanke, although certain bits of dialogue clearly aimed at isolationist forces in America were toned down or eliminated. Yet the approach was seen as a good way to fulfill a strong urging by the British Minister of Information, Alfred Duff Cooper, for Hollywood studios to produce patriotic, pro-British stories. Beyond the appeal to higher values, it didn't hurt that Cooper was certain British audiences would eagerly flock to the cinemas for such productions.

Studio archives contain a number of memos from Wallis to Curtiz detailing the production chief's dissatisfaction with the director's handling of many scenes in his previous films with Flynn Captain Blood, The Charge of the Light Brigade (1936), and The Adventures of Robin Hood. Attempting to avoid such conflicts and misunderstandings on The Sea Hawk, he spent several hours with Curtiz in July 1939 going over Koch's script scene-by-scene. However, production delays on the Curtiz-Flynn Western Virginia City pushed back casting tests for The Sea Hawk to January 1940.

Flynn had played an English adventurer opposite Bette Davis's queen in The Private Lives of Elizabeth and Essex (1939), but the monarch role in The Sea Hawk's script was too small for the studio's top female star. Flora Robson had played the role to much acclaim in the British film Fire Over England (1937). Her January 1940 test for the Warners picture was successful, but she was unwilling to take the part because of a theater offer that came to her around the same time. Curtiz eventually persuaded her to do the movie by promising to shoot her scenes first so she could take on the stage role.

By this point, Errol Flynn was the studio's top male star, bringing in more at the box office than any others on the roster, but he felt that he was not given the same deferential treatment as some of his colleagues. Flynn always felt ill-treated by the studio and was at frequent loggerheads with Jack Warner, who ran the West Coast operation. Warner, in turn, was tired of the constant problems he had with his star. Attempting to scare him into line, the studio tested contract player Dennis Morgan for the role, but it was never really going to be anyone else's picture but Flynn's––and he knew it.

In March 1940, while The Sea Hawk was already in production, Seton Miller raised a fuss over Howard Koch's determination to receive sole screen credit for the script. In a letter to the studio dated March 18, 1940, Miller outlined the similarities in the two scripts, noting a few minor details added by Koch, such as a softening of the characterizations of Elizabeth and the two villains, a change in the nationality of the servant of the Spanish noblewoman, and the addition of a pet monkey for Flynn's Captain Geoffrey Thorpe. Miller conceded that Koch had tightened the structure of the story, shortening some scenes, eliminating others, adding a few new ones, and changing some of the dialogue. But he also insisted the meaning of the dialogue was the same and in some cases lifted wholesale from his own script, while the basic story and characters were all present in Miller's version. He suggested that fair credit would be Original Story by Seton Miller (since, contrary to the studio's initial decision to include Sabatini's name, the screenplay had nothing to do with the original novel) and Screenplay by Koch and Miller. A couple days later, Koch countered that while Miller was correct in many of his facts, he was mistaken in "most of his conclusions." Koch also insisted he did not want sole credit but that he did feel he should get top billing. By the end of that week, Miller agreed to take second screenplay billing and not go into arbitration. The studio also dropped Sabatini's name from the credits.

by Rob Nixon