Kai, this sentiment is actually a load of bunk, maybe an attempt to placate Canadians but hardly a rehearsal for D Day [img]graemlins/no.gif[/img] .
It was one in a series of Combined Operations 'Great Raids' - great as in size. It was application of a theory on how to capture a fortified port by frontal assault. In that it provided lessons for D Day, but hardly how to land 150'000 men on a massed front. The lesson learnt BTW, was simply don't.
Before D Day, the Allies had experience of N. Africa, Salerno, Taranto and Anzio. These were not 'rehearsals' for 6th June if you wish?
No.9