The public is probably less aware of the key Canadian connections to this wartime effort. Beyond the fact that Canadian scientists were involved south of the border (notably Walter Zinn of Kitchener, Ontario, who helped build the first nuclear reactor in Chicago, and a number of others to follow), and that Canada supplied crucial materials like uranium and heavy water to the effort – there was also an entirely 'other' secretive government laboratory, at Chalk River, Ontario, essentially designated as a satellite operation.

The story of the Chalk River lab actually begins well before the Manhattan Project – rooted in the early work of French scientists to master nuclear fission, and the work of British scientists that first confirmed its unprecedented bomb potential.

Building on the groundbreaking work of Canadian scientist George Laurence, who – shortly after fission's discovery in 1939 – had built one of the world's first nuclear reactors in downtown Ottawa (pre-dating Fermi by a couple of years, albeit without his ultimate success), the British and Canadian governments established a nuclear lab at the University of Montreal in Quebec. It was here, at the end of 1942, that both the French and British nuclear programs were consolidated, away from the Germans and close to the Americans: the giant south of the border was now unshackled, in the war, and taking the lead on nuclear matters.

The focus of the 'Montreal Lab' was a specific challenge of nuclear science that even the resources of the Manhattan Project would not solve in time to impact the war: a high-powered heavy-water reactor for making plutonium.

Plutonium did not exist on earth before the war (at least beyond trace amounts), but quickly became one of the most sought-after and closely-guarded ingredients of modern warfare. To make plutonium you needed a reactor, and a heavy-water reactor was known to be the best way to do this – in theory at least. In practice you could get the job done quicker and cheaper at the time with an alternate material, graphite, and this became the focus of the US efforts.

One of heavy water's problems was its scarcity. A rare component of ordinary water (less than a gram per litre) discovered only a decade earlier, barely 200 litres of the material existed on the planet.

Nevertheless, with this prized inventory in hand as 'starter' material (whisked secretly out of the labs in Nazi-occupied France), the Canadians, French, and British scientists set to work in Montreal, and soon chose a secluded spot on the Ottawa River in Ontario as their 'Los Alamos'.

Here they built what later became known as Chalk River Laboratories, plus a nearby townsite, poetically named 'Deep River', that would house the scientists and their families – both locations, like Los Alamos, kept secret until after the war.

The 'Robert Oppenheimer' of the Canadian project was John Cockcroft – eminent British physicist, future Nobel laureate (ironically, for splitting the atom over a decade earlier, albeit with an accelerator and not through fission), and eventual leader of Britain's post-war nuclear program.

Under Cockcroft's direction the Canadian project laid the foundations for a massive heavy-water research reactor, the National Research eXperimental (NRX), along with a smaller, low-powered cousin, Zero Energy Experimental Pile (ZEEP), to aid in its development.

They also designed and built a complex process to separate plutonium from irradiated nuclear fuel, independent of the secretive process developed under the Manhattan Project – an early sign that the atomic genie was free of its bottle and walking the earth, and making friends.

Meanwhile the war ended, the British and French scientists went home, and Canada found itself with the second-largest nuclear program on the planet.

With ZEEP starting up in September 1945, Canada became the second nation to control the atom.

With the massive NRX reactor starting up in 1947, Chalk River operated the most powerful research reactor in the world – now under the scientific direction of Wilfred Bennett Lewis (like Cockcroft, a British physicist and former protégé of the legendary Ernest Rutherford).

Nuclear leadership was an objective of the Canadian government when it famously answered "okay, let's go!" to the 1942 British proposal that became Chalk River (the quote attributed to Clarence Decatur Howe, wartime Minister of Munitions and Supply). If Canada began the 20th century as a resource-based economic lightweight, it emerged from the exigencies of WW2 an industrial powerhouse – and, as it happened, poised to light the way for science as well.

This torch was lit by the wily scientists who first sketched out the NRX reactor: funded by war, it was designed for peace. With little knowledge of where exactly the science would lead, they built the biggest, most flexible machine they could – enabling, within a decade of the war's end, the gift of cobalt cancer therapy and nuclear medicine, unprecedented insights into the structure of matter, safer and stronger materials, and Canada's launch to the forefront of nuclear power development (including testing the fuel for Nautilus, the world's first nuclear-powered submarine, under operating conditions).

And Canada continued to provide plutonium to the US military for almost two decades after the war, halted eventually by evolving export policy.

By the mid-1950s the mightier National Research Universal (NRU) reactor, ten times the power of NRX, came online at Chalk River, and both machines propelled the Canadian nuclear program through the next decades – culminating in a fleet of Canadian-designed heavy-water power reactors (CANDU) that are among the safest and most efficient on the market, and today largely responsible for the province of Ontario operating an almost carbon-free electricity grid.

John Steinbeck noted that "all war is a symptom of man's failure as a thinking animal", but it can also be an accelerant of thought, and technical progress. When Canada became the first country with the ability to build an atomic bomb but chose not to, it charted a path of leadership in nonproliferation that it followed into this century. As a species our failures have also followed us, unfortunately.