The feared Jolly Roger of the 18th century is intrinsically linked with the swashbuckling sea pirates of old.
Historically, the flag was flown to frighten pirates' victims into surrendering without a fight, since it conveyed the message that the attackers were outlaws who would not consider themselves bound by the usual rules of engagement. As piracy declined - it nonetheless remained as an ominous symbol of lawlessness and violence.
It's appropriation into naval warfare is an interesting insight into the unique culture and nature of submariners.
In 1920, Admiral Sir Arthur Wilson VC was appointed to the position of First Sea Lord of the Royal Navy.
The advent of the Submarine in Naval Warfare was not without detractors.
Ironically, Sir Wilson was one of them. He branded submarines as being "Underhand, Unfair and Damed Un-English". He is said to have spoken to the British Admiralty to have the crews of enemy submarines captured - tried and hanged as pirates.
Admiral Wilson's statement instigated and was acted upon by a then young Lieutenant Commander, Max Horton. Horton was the Commanding Officer of HMS E9. His E-Class submarine was the first to fly the Jolly Roger on her return to port after sinking the German cruiser SMS Hela and the destroyer SMS S-116 in September 1914.
This fine tradition stuck and carried on throughout WWI and all the way through WWII.
The Jolly Roger as appropriated by the Submarine Captains became enduring legacies of the heroics of these brave crews during combat, who taught with the proverbial touchness of pirates.
Each flag as hoisted would announce via coded inferences that submarines victories against the enemy.
Jolly Rogers were usually made from blackout material and semaphore flags, cut up to make the different symbols.