The mass circulation media in Canada recently expressed some surprise at a Canadian vote against a resolution in the UN disarmament committee. The resolution called for a phased program of nuclear disarmament leading to "eventual elimination of these weapons within a time-bound frame work". The surprise was somewhat assuaged by the competing resolution, co-sponsored by Canada, which urged systematic and progressive efforts to reduce nuclear weapons globally "with the ultimate goal of eliminating these weapons." Canada's position as a peacekeeper and moral guardian of the West was probably the basis for the media's surprise. Certainly, Canada has emphasized its role as a peacekeeper, especially in nuclear matters. For example, in an "agreed declaration" with the United States and Great Britain in November 1945, Canada stated it supported action "to prevent the use of atomic energy for destructive purposes" and to promote its use for "peaceful and humanitarian ends". Of course, a question arises as to why Canada was included with the United States and Great Britain in such a declaration; that question is answered, albeit in a subtext, in Richard Rhodes's important new book.
In an earlier work, The Making of the Atomic Bomb, Mr. Rhodes took the reader through the development of the atomic bomb, leading to the destruction of Nagasaki and Hiroshima. The present book extends this history forward to the development of the hydrogen bomb and, in a somewhat more cursory fashion, to the Cold War and its eventual ending.
In common parlance little distinction is made between an atomic and a hydrogen bomb. The distinction in terms of physics, however, is significant and the difference in potential yield enormous. An atomic bomb, such as those used on Hiroshima and Nagasaki, works on the principle of atomic fission. Specifically, the energy released in it comes about from the breaking apart of higher into lower atomic number elements. These devices can be horrifically destructive. But their power tends to be limited to the equivalent of kilotons, as opposed to megatons, of TNT. Hydrogen weapons, on the other hand, work on a principle of atomic fusion, in which hydrogen atoms fuse to form heavier atomic elements. The amount of energy released is effectively unlimited and can extend into the tens of megatons of TNT equivalence. Accordingly, a Nagasaki-scale bomb has a fireball of about 800 yards across, whereas "Mike", an early test hydrogen bomb, had a fireball larger than three miles in diameter.
Although the world was profoundly shocked at the destruction in Hiroshima and Nagasaki, it may be that the additional fire power created by the atomic bombs could have been incorporated into war as waged during the 1940s. Atomic weapons differed in degree, and not kind, from the bombs that burned Tokyo. That, clearly, was not the case with the vastly greater destructive force of hydrogen weapons.
Mr. Rhodes's book traces the evolution of the hydrogen bomb programs led by the United States and the Soviet Union with considerable care and detail. Until the dropping of atomic weapons on Japan, the scientists working on the Manhattan project had little if any significant discussion on the appropriateness of proceeding with their research. The well-known recommendations on the use of nuclear weapons from a committee of scientists at Los Alamos (including Fermi and Oppenheimer) in June 1945 (easily available on the Internet) evinces some concern at their use, but no regrets for their development.
The general consensus that defeat of the Axis powers was crucial to the continuation of society assuaged concerns over the morality of the development of atomic weapons. After the surrender of the Japanese empire, however, the defeat of international fascism, together with influential anti-nuclear articles in, among other places, the New Yorker, led to a general cooling of scientific enthusiasm for the development of hydrogen weapons.
As is very well set forth in Mr. Rhodes's book, the actual physics of proceeding to a hydrogen weapon were poorly understood and, indeed, could not be determined until technical advances, particularly in calculating equipment, were made. The very first electronic computers designed during and following the war, the ENIAC and the subsequent MANIAC, were driven by a need for more calculating power to permit the development of hydrogen weapons. In 1947, Edward Teller (the brilliant if mercurial Hungarian scientist who was, with Stanislaw Ulam, the creator of the first hydrogen bomb) had proposed holding off work on the hydrogen bomb project for at least a year, to allow further development of computing power and, specifically, the completion of the MANIAC.
Once that computing power was in place, it rapidly became clear that the early proposals could not work. These had suggested using an atomic bomb to act as a mechanical trigger for the hydrogen bomb. This was misguided in physical terms. When an inspiration came to Teller and Ulam in late 1950 to use radiation pressure (still from an atomic bomb) to ignite hydrogen in a fusion burn, the new computing power made it clear that a hydrogen bomb was feasible. Further, the new computers were needed to turn the Teller-Ulam concept into a functioning device; without them, the hydrogen bomb could not have been built, or at least would have been much greatly delayed.
By contrast to Western hesitation, the Soviet Union eagerly pursued the development of hydrogen weapons and Soviet scientists expressed no significant qualms. Obviously, even had they wished to oppose it, they were in no position to do so. One did not refuse Stalin or his special nuclear emissary, Beria. But they did not pursue atomic and hydrogen weapons solely out of fear of their leaders. The opinion among Soviet scientists was that unless the Soviet Union caught up to the United States there would ultimately be a war in which their country would be laid waste by Western powers with nuclear weapons. Certainly, some of the rhetoric and actions of Western leaders gave a ring of truth to those concerns. The US Strategic Air Command, through the early 1950s and even to some extent through the Cuban missile crisis, pushed for a pre-emptive nuclear strike on the Soviet Union. This inclination was known to the Soviets, as were continuing overflights of their airspace, which were, in themselves, acts of war.
With these motivations to force them forward, Soviet scientists, helped by an almost miraculously competent spy network, rapidly developed both atomic and hydrogen weapons. The scale of Soviet espionage is staggering. Information reached Moscow at roughly the same time it reached Western leaders. When Igor Gouzenko tried to defect in Ottawa in the fall of 1945, he was at first refused by no less a person than Mackenzie King, who seemed to think the story of massive Soviet spying to be beyond belief. As King later discovered, Gouzenko had told only a small part of the story. Early Soviet atomic weapons were almost exact copies of Western bombs, but after early success, the Soviets began to pursue somewhat different roads to increased yields. The initial Soviet hydrogen bomb design was simpler than the American one and fairly limited in its potential yield. But for world opinion, a hydrogen bomb was a hydrogen bomb and the Soviet Union had caught up with the West.

Canada's role in the development of the modern nuclear industry, including the development of weapons, was far from insignificant. That is why Canada, together with the United States and Britain, signed the agreed declaration in late 1945; at that time only the United States, Britain, and Canada had the knowledge available to build atomic weapons.
The country's role in the nuclear sciences began before the turn of the century with Ernest Rutherford's 1898 experiments into atomic structure, in Montreal. Today, Canada remains a nuclear leader; sixty percent of Ontario's electricity is produced by nuclear power, and thirteen Canadian CANDU nuclear power plants operate outside North America, generally in Third World countries. The first self-sustaining nuclear pile outside the United States was initiated at Chalk River, near Ottawa, in September 1945. Chalk River Laboratories is a "world-renowned [research] facility", according to Atomic Energy of Canada Limited literature in 1995. This is unquestionably true. But the AECL material does not say that Chalk River was founded during the Second World War as part of the project to build atomic bombs, the Manhattan project, and that its first role was to produce materials for those bombs.
Canadian researchers in Montreal were fully integrated in the Manhattan project and Montreal was considered as the site of the third heavy water production facility. The Canadians had such complete access to the project's materials that, at the very end of the war, United States military authorities started to restrict information going to Montreal, because of concerns that Canada could (or would) build its own atomic weapons. Certainly, the full integration is shown by the appointment of Carson Mark, a Canadian, as head of the Los Alamos theoretical division just after the war. Perhaps the most striking sign of Canada's role in the early days of atomic weapons was the requirement that the United States, Britain, and Canada all consent to the use of nuclear weapons on Japan in 1945; this consent was sought and given. The Canadian veto was lost shortly after the war, but its very existence is now startling.
On the other hand, our role in the early atomic bomb program can be overstated. After all, Canada was considered by its allies, at least during the war, more as a bridge between the United States and Britain than as a sovereign state. In such a position, Canada's having been an integral part of an Anglo-American atomic bomb project is not surprising. This work may well be seen as just another aspect of the country's heroic role in the Second World War; that said, it is a fascinating and little-known sideline of history and one of many reasons why Mr. Rhodes's book is well worth reading.