A steel lock gate several meters thick, designed to withstand any attack, was driven ten meters inward by the impact of a metal hull moving at full speed. This was not a scene from a Hollywood war film, but a real event that occurred along the banks of the Loire during one of the boldest nights of World War II. A handful of men, an old ship destined for scrapping, and a carefully concealed quantity of explosives were sufficient to permanently disable one of the most strategically important port infrastructures of the Atlantic. The HMS Campbeltown, originally the U.S. Navy destroyer USS Buchanan, was loaded with 4.5 tons of explosives hidden in a concrete casing before it ran aground on the Joubert lock gate on March 28, 1942. The mission was to destroy the only dry dock in the Atlantic capable of accommodating the German battleship Tirpitz, thereby preventing its repairs. The delayed explosion, which occurred ten hours after the ship ran aground, rendered the lock unusable until 1948, at the cost of 169 deaths and 215 prisoners among the 600 commandos involved. The HMS Campbeltown was originally an American Wickes-class destroyer, named USS Buchanan, transferred to the Royal Navy under the Destroyers for Bases agreements between Washington and London. This trade of military bases for old warships allowed the British navy to recover about fifty American destroyers, including this ship that would experience a spectacular end to its career. To carry out the operation, British engineers disguised the ship to appear like a German torpedo boat, a disguise intended to deceive enemy lookouts during the crossing of the English Channel. However, the most critical aspect was invisible to observers: in a concrete casing hidden within the hull, the British had placed 4.5 tons of delayed-action explosives. The old destroyer was no longer a conventional warship; it had literally become a floating giant bomb, programmed to strike at the most unexpected moment. Saint-Nazaire became the target of this operation, named Chariot, not by chance. The port housed the Joubert lock gate, the only dry dock in the entire Atlantic capable of accommodating a ship as colossal as the German battleship Tirpitz. For the British high command, the threat was clear: if the Tirpitz were damaged during a sea sortie, it could retreat to Saint-Nazaire to be repaired before setting out again to sow terror among Allied convoys in the North Atlantic. Depriving Germany of this single dry dock effectively neutralized the Tirpitz itself, condemning it to never venture too far from its home waters without taking a huge risk. On the night of March 27 to 28, 1942, the HMS Campbeltown ascended the estuary of the Loire, escorted by a flotilla of small motorboats carrying British commandos. Despite the intensifying coastal defense fire as the convoy approached, the destroyer maintained its course and crashed into the Joubert lock gate at an impressive speed of 20 knots, driving it inward by nearly ten meters. Once the ship was stranded, the commandos disembarked to sabotage the port's auxiliary installations, in a frenzy of hand-to-hand combat and crossfire in the darkness. The human toll of this night is extremely heavy: of the 600 men involved, all volunteers, 169 will be killed and 215 taken prisoner. Only 227 of them will eventually return to Great Britain, often at the price of a perilous escape through occupied France. The delayed explosion that changed the face of naval warfare. The real coup de théâtre of Operation Chariot does not occur during the battle, but after. Convinced they were dealing with nothing more than an inoffensive wreck, German soldiers boarded the Campbeltown to inspect it in the hours following the attack. It is precisely at this moment that the trap mechanism closes: ten hours after the ship ran aground, the explosives hidden in the concrete casing detonate, blowing up the ship and killing the soldiers present on site. The Joubert lock gate, literally pulverized, renders the lock completely unusable. Despite several repair attempts by the occupying forces, the installation remains out of service for the rest of the war and does not become operational again until 1948, officially recommissioned in 1950. The remains of the destroyer are not removed from the basin until 1947, five years after the explosion. It was not until March 1978 that the first physical relic resurfaced: a 76-millimeter forward gun, recovered during a dredging operation in the port and now displayed on the panoramic terrace of the fortified lock. More recently, in 2020, a door from the destroyer was found during port work, a piece visible since the end of March 2024 at the Le Grand Blockhaus museum.