The film is a historical drama set during the reign of Elizabeth I (Flora Robson), focusing on the English defeat of the Spanish Armada, whence the title. In 1588, relations between Spain and England are at the breaking point. With the support of Queen Elizabeth I, British sea raiders such as Sir Francis Drake regularly capture Spanish merchantmen bringing gold from the New World.

Cagney is a human dynamo as a drifter who helps save ailing Grace George from losing her newspaper. The pace is fast, and audiences of all ages will be pleased. The supporting cast, have all the small-town characterizations down pat — with Margaret Hamilton a standout. Cagney himself, had genuine affection for this film, and listed it among his top five movie-making experiences at a retrospective the year before he died.