I'd never even heard of this event before but it was absolutely amazing. Operation Chariot was the commando raid on the Turpitz's berth @ a submarine base in France. The only problem was that the target was so heavily defended that they couldn't bomb it from the air or hit it with ship artillery or submarines.
So they disguised an old lend-lease destroyer as a German ship and sent in the commandos and tons of high explosive.
Combined Operations examined a number of options while planning the destruction of the dock. At this stage of the war the British government still tried to avoid civilian casualties. This ruled out a bombing attack by the RAF, which at the time did not possess the accuracy needed to destroy the dock without serious loss of civilian life.[7] The Special Operations Executive were approached to see if its agents could destroy the dock gates. They decided that the mission was beyond their capabilities because the weight of explosives required too many agents just to carry them.[8] The RN were also unable to mount an operation, as St Nazaire is 5 miles (8.0 km) up the Loire Estuary. Any naval ships large enough to cause sufficient damage would be detected well before they were within range.[7]
The planners then examined whether a commando force could be used. There was an unusually high spring tide due in March 1942, which would allow a light ship to pass over the sand banks in the estuary and approach the docks, bypassing the dredged and presumably well-defended channel. It would still be too shallow for infantry landing ships, but specially lightened destroyers might succeed.
http://en.wikipedia.org/wiki/St_Nazaire_RaidHMS Campbeltown was a "Town"-class destroyer of the Royal Navy during the Second World War. She was originally the American destroyer USS Buchanan, and, like many other obsolescent U.S. Navy destroyers, she was transferred to the Royal Navy in 1940 as part of the Destroyers for Bases Agreement.
She was transferred on 3 September 1940 and commissioned on 9 September at Halifax, Canada.
Lend-lease was signed into law on March 11, 1941
