The destruction that HMCS Haida wrought upon the German navy during the Second World War is well-documented — but the famed Canadian destroyer's behind-the-scenes role helping plan for the Normandy landings was also a crucial part of the effort, says the ship's longtime historian.

Peter Dixon, director of history with Friends of HMCS Haida, said it's important to laud the destroyer's numerous battle victories, which include sinking nine vessels between April and September of 1944 — the most of any Canadian ship. But Dixon says revelations made in recent years show the ship played a vital role testing technology that would help trick the Germans into expecting invasion at Pas de Calais, hundreds of kilometres north of the eventual landing site in Normandy.

"Haida's role in D-Day is actually pretty cool," said Dixon, who has been working with the tribal-class destroyer in various capacities since 1968. "It was kept secret for so long. This stuff is really only coming out in the last 10 years… What Haida was doing, you could make an argument that it was the start of (electronic intelligence) warfare. Haida was on the cutting edge."

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That May, leading up to the June 6 Normandy landings, Haida participated in a secret exercise in Edinburgh known as Operation Moonshine, said Dixon. The destroyer towed a massive barrage balloon — something like a floating blimp — in the water, while Stirling bombers dropped aluminum foil strips that bounced off the balloon.

"The effect this had on shore radar was startling," said Dixon, noting the operation also tested radar-jamming techniques. "It gave the picture of hundreds of contacts; ships incoming."

The test was a success, and the technique was used by other ships June 6 to impersonate an incoming naval attack at Pas de Calais, overwhelming the Germans' onshore radar.

"That deception was very effective," said Dixon, noting Germany's Panzer tanks were stationed in Pas de Calais. "Those Panzers would have done major damage if they had been released to Normandy."

When it wasn't conducting secret planning exercises, Haida — now a Parks Canada destination moored at the foot of Catharine Street North — was patrolling the English Channel for much of 1944. Now known as this country's "fightingest" warship, a title based on surface-tonnage sank, Haida is the only remaining Tribal-class destroyer out of 27 built for Britain, Canada and Australia in the 1930s and 1940s.

Destroyers were designed as fast-moving attack vessels that could target larger ships, but their operators soon found they were so flexible they could "almost do anything," said Dixon.

"Their basic tenet was to protect the battlefleet," he explained. "The Tribals were designed to be the defensive force of the battlefleet (and) were the most heavily armed destroyers in World War 2… Whatever Haida aimed her guns at, it was destroyed."

On April 26, Haida sank a German torpedo boat, which were comparable to destroyers. A few days later, the ship was part of the battle that saw the loss of HMCS Athabaskan, a fellow Tribal-class destroyer in the Royal Canadian Navy, known as Haida's "twin sister." That day, April 29, they were fighting several German ships off the coast of Saint-Brieuc, near the western end of the English Channel, when Athabaskan was struck, going down in five minutes with 128 men on board.

Haida managed two simultaneous ship-to-ship gun battles with different German ships before chasing one ashore and destroying it with gunfire. Commander Harry DeWolf then returned to rescue 47 Athabaskan crew members, at great risk to his ship and crew.

"You had a job to do and you didn't really think about it until after," Haida radar operator Bob "Rabbit" White told The Spectator in 2005, describing the battle. Opening the door of his radar cabin amid the shooting, he saw an enemy shell coming straight for him and slammed the door closed. The shell missed the ship, passing between Haida's funnels. "I suppose it was close."

On D-Day, Haida and its Tenth Destroyer Flotilla were stationed off Ushant, an island off the western tip of France, ready to intercept any German vessels that came their way. On June 9, an enemy convoy arrived, with Haida sinking two destroyers and helping to prevent the Germans from accessing the Normandy beaches.

"That battle was very significant," said Dixon. "Those were the only attempts by German forces to try to get to the invasion, and they were stopped."

On June 24, Haida destroyed the tower of a German submarine that surfaced in the channel, forcing the crew to abandon ship. The 23 German seamen were picked up by Haida and its patrol partner HMS Eskimo, in the only time the ship would take prisoners aboard.

"The prisoners were put in the forward, lower mess deck and it was locked," said Dixon, adding they were only aboard for about four hours until Haida returned to England, where it was stationed. On the way back, crew members of British cruiser HMS Black Prince reportedly complemented DeWolf on successfully hitting the u-boat, an unusual target for a destroyer. DeWolf, perhaps wryly, responded that the high-intensity outing was "just morning recreation for the crew."

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Respected by his officers and crew, DeWolf was known as "Hard-over Harry" — a term referring to the sharp turns required to make evasive action in battle. He was about 40 years old at the time of the war, an old man in military years. (For comparison, the captain of the Athabaskan, John Stubbs, was 27.)

"DeWolf was Canada's Nelson," said Dixon. "Harry became our greatest naval officer for Haida. Haida went through all her engagements, and only received six 20-millimetre rounds — one of which went into the captain's cabin and destroyed Harry's golf clubs. It got Harry highly motivated to sink ships… At 80, he was still golfing his handicap.

"He was highly regarded by his crew. They would have gone with him wherever."