As soldiers began dying in droves, a small group of Prairie soldiers embarked on a stealthy mission to prevent such a tragedy from happening again.
The troop of 10 men from the South Saskatchewan Regiment were assigned to offer protection for a British radar expert on a mission to cripple German radar systems.
Historians remember Jack Nissenthall as someone who had distinguished himself in the 1930s as he worked alongside the RAF suggesting modifications to British systems.
Radar _ or an acronym for Radio Detection and Ranging _ was still a fledgling technology on Aug. 19, 1942, said military historian Michael Bechthold of Wilfried Laurier University.
Despite its novelty, the tracking systems had already proven their value to British forces during the Battle of Britain when they were used to detect air raids from the Luftwaffe, Bechthold said.
"With the radar, they were able to detect the Germans before they got there, which gave them the chance to get their Spitfires and Hurricanes up the air to deal with them."
While historical accounts differ widely on the outcome of Nissenthall's mission at Dieppe, they concur on the details.
Nissenthall was tasked with physically infiltrating the German radar system known as Freya located between Dieppe and Pourville. The objective was to determine the type of system the Germans were relying on or die trying.
Orders for his Canadian body guard were similarly succinct _ Protect him. If he faced imminent capture, shoot him. Nissenthall simply knew too much about British radar to be left in enemy hands for interrogation.
Like much of the raid on Dieppe, the group's mission did not go according to plan. Bechthold said a navigational error landed the boat carrying the team on the opposite side of the Scie River from where they were supposed to disembark.
While backtracking to get into position, the team soon found themselves overwhelmed by German firepower. The patrol had managed to come close to their target, but realized they would never make it into Freya itself as expected.
Plan B was born on the spot, according to James Leasor's 1975 book "Green Beach." Nissenthall believed he could force the Germans to share their radar findings over radio channels if he could successfully cut the phone wires snaking toward the station.
Those radio transmissions could be monitored in Britain, giving the Allies clearer knowledge of what the enemy could and could not see on their radar screens.
According to Leasor, Nissenthall shinnied up towards the wires in a hail of bullets, severed the necessary lines and plunged to the ground after completing his final cut.
Nissenthall got back to the beach in safety, but without most of the Canadians who had accompanied him on the treacherous sortie. Bechthold said all but one of his guard made it back to England. The fates of the others are not definitively known.
The impact of Nissenthall's actions is a source of debate. Leasor claimed details from the radio transmissions provided vital information that fuelled Allied battle plans for years after Dieppe.
Bechthold argued the triumph wasn't quite so clear-cut. While Nissenthall was able to identify the type of equipment in use at Freya based on the aerials he had seen up close and give British troops a few days worth of access to radio transmissions, Bechthold said that information alone was not enough to be a game-changer for the war effort.
"It would have aided the process, it would have given them an indication of where to go and what to do, but it wasn't the simple cause and effect kind of thing that Nissenthall and others are claiming," he said.
The stealth radar operation is hardly the first aspect of the Dieppe raid to be the subject of scholarly controversy.
A new documentary set to be released this weekend purports to make new revelations unearthed by military historian David O'Keefe. The film, which airs on History Television on the anniversary of the raid, argues the entire Dieppe operation was intended as a massive diversion that would allow top secret British forces to gather code intelligence from a German military post.
The suggestion was a diversion for various intelligence gathering missions also surfaced in 1976 in "A man called Intrepid," the best-selling biography of Canadian spymaster William Stephenson.
In 1978, Nissenthall shortened his name to Nissen and immigrated to Canada. A year later, in a letter to the Globe and Mail, he wrote of his role in the war and praised the sacrifice of the Canadians at Dieppe.
“I would like to say that, without the sacrifice of that army of heroes, we would have been utterly defeated on D-Day," the letter concluded. "We were all lined up to make every mistake in the book. It is still not too late to say thank you…”
A delegation that includes some Canadian veterans who participated in the raid was to take part in ceremonies on Sunday in the French port to mark the 70th anniversary of the raid.