During World War II, German submarines are sinking thousands of tons of British merchant shipping. British intelligence, based in India, believes that information is being passed to the U-Boats by a radio transmitter hidden on board one of three German merchant ships interned in Goa, then a colony of Portugal. Portugal was neutral during the Second World War; the ships cannot be attacked by conventional forces.
The head of the Indian section of Special Operations Executive authorises attempts to kidnap and interrogate two known German agents, but these operations both fail. An approach is then made to a territorial unit of British expatriates, the Calcutta Light Horse, to carry out the mission on its behalf. They all volunteer – all are trained in military skills and keen to 'do their bit'.
Whilst the volunteers are trained, Stewart and Cartwright travel covertly to Goa. By a mixture of blackmail and bribery, they arrange diversions on the night of the raid. A party is to be held in the Governor's palace, a brothel will offer free entry to sailors from the German ships and a fiesta will be held. Stewart has a brief affair with Mrs.Cromwell, a mysterious and socially well-connected woman, who turns out to be a German agent and the main conduit for information, known to the Germans and the British by the code-name Trompete (Trumpet). She is eventually killed by Stewart, after she attempts to kill him.
The raiding party sail around the coast in a decrepit and barely seaworthy barge; they set mines on the hull of the German ship in Goa. They then board, catching the depleted crew off-guard. Despite Pugh's order that there be no shooting, several German sailors are killed. The ship is set alight and the party withdraws, watching as the ship sinks.
The title music for The Sea Wolves was adapted by Roy Budd from the famous Warsaw Concerto of composer Richard Addinsell. Budd had, at the time, already composed or arranged numerous other film scores, notably those of The Wild Geese and Get Carter. For The Sea Wolves, Budd added lyrics by Leslie Bricusse to his, Budd's, arrangement of the Warsaw Concerto music, the resulting song being entitled The Precious Moments, sung by the British baritone Matt Monro, who had also sung title tracks for many other films.
The Sea Wolves was, in fact, based on more than one clandestine operation of the Second World War. Some details of the film accord closely with those of Operation Postmaster, a January 1942 naval Special Operations Executive (SOE) raid on shipping in the harbour of Santa Isabel (now Malabo), on the island of Fernando Po, a Spanish (and therefore neutral) possession in the Bight of Biafra. Fernando Po (renamed Bioko) is now part of the republic of Equatorial Guinea.
SOE undertook the Fernando Po operation in collaboration with the Maiden Honour Force, which was then under its control. That force, commanded by Major Gus March-Phillipps, was the precursor to the later and larger Small Scale Raiding Force (SSRF), which was placed under the orders of the Combined Operations Command.
In the film, Trevor Howard's character arranges for the bordellos of Goa to be open and free of charge for the crews of the German target ships, in order to distract them. This was also the case in Operation Postmaster, in which, also, an SOE officer living on Fernando Po, Richard Lippett, operating under commercial cover as an employee of the Liverpool shipping enterprise John Holt & Co, persuaded the wife of a prominent German resident to hold a drunken party for the German and Italian ships' officers. In the film, a Portuguese official is suborned by British officer Roger Moore and arranges for a glittering reception held under the aegis of the Governor of Goa, for much the same purpose.
A further similarity between the events of Operation Postmaster and the plot of The Sea Wolves was that the main rationale in both was that of hitting German U-boat operations, though in Operation Postmaster, the enemy ships were not destroyed but captured and then towed to Lagos in British-ruled Nigeria, "a flagrant act of piracy".
The Fernando Po/Operation Postmaster job was but one of a number of creative operations (some successful, some not) launched by SOE, particularly in the earlier part of the Second World War.
As far as the (real) Goa mission, Operation Creek, is concerned, the Calcutta Light Horse embarked on the barge Phoebe at Calcutta and sailed around India to Goa. After the German ship Ehrenfels was sunk in March 1943 by the team of British saboteurs, British intelligence dispatched an open message over the air, warning (falsely) that the British intended to invade Goa. The crews of the other two German merchant ships in the harbour, the Drachenfels and Braunfels, received that message and scuttled their ships in Goa's harbour in the belief that they were protecting their ships from capture by the British. Italian ships in the harbour were also destroyed.
The film notes, in its closing credits, that during the first 11 days of March 1943, German U-boats sank 12 Allied ships in the Indian Ocean. But, after the Light Horse raid on Goa, only one ship was lost during the remainder of the month.
The film was originally known as Boarding Party. According to the documentary The Last of the Gentleman Producers, producer Euan Lloyd says that he originally planned to reunite Moore with Wild Geese co-stars Richard Burton and Richard Harris as Pugh and Grice.
Fifty percent of the budget was provided by Lorimar. They fell out with United Artists, their distributor, before the film was delivered. Lorimar subsequently formed a new relationship with Paramount but producer Euan Lloyd thought that studio regarded the film as "the poor cousin" and as a result it "wasn't sold properly".
The film reunited much of the cast and crew from 1978's The Wild Geese, including actors Roger Moore, Kenneth Griffith, Jack Watson, Percy Herbert, Patrick Allen, Brook Williams, Patrick Holt and Terence Longdon, writer Reginald Rose, producer Euan Lloyd, director Andrew V. McLaglen, designer Syd Cain, and composer Roy Budd.
Gregory Peck and David Niven had worked together on the 1961 film The Guns of Navarone, but were excluded from appearing in the 1978 sequel Force 10 from Navarone since it was felt they were too old to convincingly play military veterans. This film made two years later disproved this theory. Incidental music is from the Warsaw Concerto.
Filming took place on location in Goa.