Operation Deadlight was a Royal Navy operation carried out between November 1945 and February 1946, after Germany’s surrender in World War II. Its purpose was to dispose of surrendered German U‑boats (submarines) so they could never return to service.wikipedia
Germany surrendered about 156 U‑boats to the Allies at the end of the war.YouTubewikipedia
The Allies decided to keep only 30 (10 each for the UK, US, and USSR) for testing and evaluation.YouTubewikipedia
The remaining 116 were marked for destruction under Operation Deadlight.YouTubewikipedia
The Royal Navy gathered the surrendered U‑boats in harbors in places like Loch Ryan and Lisahally in the UK. From there, they were towed out into the Atlantic and sunk in deep water.wikipediaYouTube
The British designated three scuttling areas, codenamed XX, YY, and ZZ, roughly 100 miles or more northwest of Ireland.YouTubewikipedia
Some U‑boats were sunk as live-fire practice targets for aircraft and surface ships, especially in the ZZ area.YouTubewikipedia
Others were scuttled by opening sea valves or using explosive charges; if that failed, they were finished off with naval gunfire.YouTubewikipedia
Weather, age, and poor condition meant many of the boats sank or broke up under tow before reaching the planned scuttling zones, so their wrecks are scattered over a wide area of seabed.youtube+1
There were political and practical reasons for destroying the Nazi submarine fleet instead of keeping or scrapping all of it.youtube+1
The Allies wanted to prevent any future German remilitarization at sea by eliminating the U‑boat arm that had waged the Battle of the Atlantic.youtube+1
Maintaining hundreds of obsolete or damaged submarines in port was costly and logistically difficult.YouTube
Dividing them up as spoils risked tensions among the Allies; a controlled destruction program was cleaner diplomatically.youtube+1
In effect, Operation Deadlight was an administrative “clean‑up” rather than a combat operation—destroying surrendered Nazi submarines rather than fighting them at sea.YouTube
By the time Operation Deadlight ended in February 1946, 116 surrendered German U‑boats had been sunk.YouTubewikipedia
This made it one of the largest deliberate, organized destruction operations of naval vessels in history.youtube+1
The U‑boats now form a vast underwater “graveyard” off the coasts of Ireland and Scotland, many of which have been surveyed by maritime archaeologists since the early 2000s.YouTube
So, while there is no record of an “Operation Dreadnaught” against Nazi ships at the war’s end, Operation Deadlight fits exactly what you describe: a coordinated Allied effort to destroy Nazi submarines once the fighting was over.wikipediaYouTube