On October 30, 1942, deep in the Mediterranean northeast of the Nile Delta, a desperate naval engagement unfolded that would fundamentally alter the trajectory of the Second World War. While high-level cryptanalysts at Bletchley Park worked tirelessly to pierce Nazi Germany’s naval communications, victory hinged on a brutal, physical struggle waged on the open sea. At the heart of this turning point were two extraordinary Royal Navy sailors—Lieutenant Anthony “Tony” Fasson and Able Seaman Colin Grazier—whose profound bravery during the boarding of the sinking German submarine U-559 cost them their lives but unlocked the unbreakable “Shark” code.
The Hunt for U-559
By late 1942, the Battle of the Atlantic and the Mediterranean supply routes were at a knife-edge. The German Kriegsmarine’s U-boat “wolf packs” were wreaking havoc on Allied shipping, guided securely by the Enigma cipher machine. In February 1942, the German Navy had introduced a more complex, four-rotor M4 Enigma system alongside new weather codebooks (Kurzsignalheft), plunging Bletchley Park back into darkness. Allied intelligence was effectively flying blind against U-boat movements.
On October 30, the British destroyer HMS Petard, alongside three other destroyers, hunted U-559 for 16 grueling hours. Subjected to a relentless barrage of depth charges, U-559 was forced to the surface by her commander, who ordered the crew to abandon and scuttle the vessel. As the German crew jumped into the water, the British destroyer closed in. Realizing the submarine was sinking, the captain of HMS Petard authorized a high-risk boarding party.
Inside the Sinking Submarine
Without hesitation, Lieutenant Tony Fasson (the ship’s first lieutenant), Able Seaman Colin Grazier, and a 16-year-old NAAFI canteen assistant named Tommy Brown leaped into the sea and swam across to the foundering U-boat.
Working in pitch darkness and near-total suffocation, with icy seawater rapidly flooding the compartments, Fasson and Grazier descended into the conning tower. While young Tommy Brown stood guard at the top of the hatch acting as a human chain, Fasson and Grazier frantically searched for codebooks and cryptographic hardware.
They managed to wrench crucial documents free—including the vital Wetterkurzschlüssel (short signal weather code) and Kurzsignalheft codebooks—passing them up to Brown, who tossed them safely into the waiting British whaler. Although they could not dislodge the heavy Enigma machine itself from its mount, the codebooks and weather cipher keys were precisely what the mathematicians at Bletchley Park needed.
The Ultimate Cost and Historical Impact
Time ran out entirely as the stern of U-559 dipped below the surface. Tommy Brown managed to jump clear just as the submarine made its final plunge, but Lieutenant Fasson and Able Seaman Grazier were trapped below. They went down with the submarine, giving their lives so that the vital intelligence could reach the surface.
The sacrifice of Fasson and Grazier—and the heroic assistance of Tommy Brown—delivered an immediate breakthrough. When the recovered documents reached Bletchley Park, they provided the critical context needed to decipher the four-rotor M4 “Shark” code. Alan Turing and his colleagues were finally able to read German naval traffic regularly, allowing Allied convoys to evade U-boat traps, establish maritime supremacy, and clear the path for the eventual liberation of Europe.
For their extraordinary valor, Tony Fasson and Colin Grazier were posthumously awarded the George Cross—Britain’s highest award for gallantry not in the face of the enemy—while Tommy Brown received the George Medal. Their willingness to step into a dark, sinking steel tomb remains one of the most selfless and consequential acts of individual bravery in military history.
Sources:
https://music.youtube.com/watch?v=Gu7FeeHuIkc
https://thehistorypress.co.uk/article/who-were-the-real-enigma-heroes
https://www.wearethemighty.com/history/three-british-divers-capture-enigma-machine-codebooks
https://www.wearethemighty.com/history/three-british-divers-capture-enigma-machine-codebooks
https://en.wikipedia.org/wiki/German_submarine_U-559
https://www.theguardian.com/world/2017/oct/20/enigma-code-u-boat-u559-hms-petard-sebag-montefiori
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