During the Second World War, the Allies hatched a secret plan to bomb three German dams. The Royal Air Force quickly formed Squadron 617, later known as "The Dambusters."

Nineteen Lancaster planes, led by a young pilot named Guy Gibson, launched the attack on May 16, 1943. The bombs breached two of the three hydroelectric dams, Möhne and Eder, causing deadly floods in the Ruhr Valley, an industrial heartland.

The codename for the weapon developed by Barnes Wallis for the mission was Upkeep, but it's better known as the "bouncing bomb."

Each plane carried one bomb. The cylinder-shaped weapons had to be dropped at a height of 18.3 metres and at a distance of about 400 metres from the dam. A successfully dropped bomb would backspin, bounce across the water over anti-torpedo nets, and sink at the wall of the dam. Nine metres under water, the hydrostatic fuse would detonate, exploding against the dam.

On the 70th anniversary of the mission, Sutherland spoke to CBC News about Operation Chastise. Now 89 years old and living in Rocky Mountain House, Alta., Sutherland is one of only three air crew still alive.

Sutherland's childhood dream of being a bush pilot was dashed by the outbreak of the Second World War. He signed up for the air force as soon as he turned 18 and while training on the Prairies volunteered for a gunnery course.

Sutherland had already flown on 25 missions when he joined Squadron 617, an elite group trained to drop a new bomb designed to bounce along the water surface and hit German dams.

The first planes departed late at night on May 16, in the light of a full moon, for Möhne Dam. Sutherland's plane, called N for Nancy, was flown by pilot Les Knight. Sutherland was the front gunner.

Only three bombs remained by the time the planes reached the large Eder Dam, undefended and nestled in the hills. Sutherland's plane eventually dropped the bomb that breached it. His plane wasn't involved in the unsuccessful bombing attempt on a third dam called Sorpe.

The mission was successful, but many lives were lost. Of the 133 aircrew involved in the raid, 53 died. On the ground, an estimated 1,300 people, many prisoners of war, were killed in the bombings and subsequent floods.

The aircrew were celebrated as war heroes. Sutherland eventually returned to Canada to marry his sweetheart.