Re: Dieppe Raid:

The attack upon Dieppe took place on August 19, 1942. The troops involved totaled 6,100 of whom roughly 5,000 were Canadians, the remainder being British Commandos and 50 American Rangers.

Of the 4,963 Canadians who embarked for the operation only 2,210 returned to England, and many of these were wounded. There were 3,367 casualties, including 1,946 prisoners of war; 907 Canadians lost their lives.

As "Daylia" mentioned the lessons learned were vital to the success of D-day, all of the following came about as direct or indirect results of the Dieppe Raid:

Mulberry Harbours
Steer clear of towns
Don't land on shingle beaches
Perform detailed and accurate beach surveys prior to landing
Requirement for specialist armour to overcome strong-points and obstacles - "Hobarts Funnies"
Improved co-ordination of joint arms operations
Improved fire control plans
Invention of Decca navigation system
PLUTO