Canada has long been closely linked with the United States' nuclear weapons program. The Manhattan Project was the product of a secret agreement between the USA, Canada and the UK, signed in Québec City in August 1943. Canada contributed help from Canadian scientists, policy supervision by C.D. Howe and uranium and fluorite from Canadian mines (other uranium sources included the American Southwest and the Belgian Congo). Since Canada had just become the recipient of the world's supply of heavy water, it was also hoped that Canada could manufacture plutonium for the bomb effort. Canadians developed a superior process for plutonium extraction, but no Canadian reactor was completed until just after the end of the war. After the Second World War, Canada became a world leader in nuclear research through its Chalk River Laboratories. The NRX reactor and a small plutonium extraction plant were built there in 1947, and supplied plutonium for the first British bomb. For the next twenty years, the Chalk River Laboratories (later incorporated into Atomic Energy of Canada Limited (AECL) ) continued to sell plutonium to the USA's military weapons program. Canadian research was shared freely with the United States and played an important role in the continued development of American nuclear weapons.
In 1956, AECL sold a commercial version of the NRX to India, called the CIRUS. The Indian government used this reactor to obtain plutonium for a nuclear test, Operation Smiling Buddha, in 1974. The Canadian government, which had since become opposed to nuclear weapons, refused to allow further sale of nuclear materials and technology to India, permitting only safety-related information to be passed by way of the CANDU Owners' Group.
With the launch of Sputnik and the new threat from Soviet missiles, the Canadian government decided to purchase the BOMARC defensive missile system. While Prime Minister John Diefenbaker agreed to buy the missiles, he balked at also taking the nuclear warheads that were needed to make the system useful. Accepting nuclear weapons into Canada became the central issue of the 1963 Canadian election, which saw Lester B. Pearson's Liberals, a party that had earlier opposed nuclear weapons, defeat the Diefenbaker government. On January 8, 1969, Canada ratified the Nuclear Non-Proliferation Treaty.
From the 1960s to 1984, there were American nuclear weapons in Canada . These were placed under dual key rules whereby both Canadian and American authorities had to authorize a launch. Pierre Trudeau, Pearson's successor as prime minister, was opposed to these missiles, and in 1971, declared Canada a non-nuclear country. The missiles were moved out of Canada. Despite the fact that the Nuclear warheads were never placed in the country, due to agreements between Canada and the United States, Canada purchased Nuclear weapons through a tactical budget of the Department of National Defence under the projects NORAD, and the Distant Early Warning (DEW) Line.
The Royal Canadian Air Force maintained a stockpile of AIR-2A Genie unguided nuclear air-to-air rockets as the primary wartime weapon on the CF-101 Voodoo all-weather interceptor after 1965. The rockets were held by detachments of the United States Air Force at the Canadian Voodoo bases, and would have been released to Canada if conflict threatened. These were removed in 1984, when the CF-18 Hornet entered squadron service and the Voodoo was retired.
The Canadian Army operated the MGR-1 Honest John nuclear surface-to-surface rocket as part of its land forces commitment to NATO. No. 1 SSM Battery of the Royal Canadian Artillery, attached to 4 Canadian Mechanized Brigade Group stationed in West Germany, maintained a total of four rocket launchers for Honest John missiles fitted with the W31 nuclear warhead between 1964 and 1970.
While it has no more permanently stationed nuclear weapons, Canada continues to allow nuclear-armed American planes and naval vessels to use Canadian facilities. There is, however, some local and popular objection to this federal policy. The port city of Vancouver is, by its own bylaws and signage, a "Nuclear Weapons Free Zone", although it is not clear if the American military vessels entering its harbour are free of such weapons, or how such a bylaw would be enforced. Canada also continues to remain under the North Atlantic Treaty Organisation's (NATO) nuclear "umbrella", although the government has attempted to modify NATO policy, particularly during the period that Lloyd Axworthy was Minister of Foreign Affairs.
During both World War I and World War II, Canada was a major producer and developer of chemical weapons for the Allied war effort. These were used in combat in World War I, but not in World War II. Human experimentation was carried out during World War II, with CFB Suffield becoming the leading research facility. Thousands of Canadian soldiers were exposed to mustard gas, blister gas, tear gas, and other agents, and some were permanently injured as a result. Human testing of weapons such as sarin and VX gas continued well into the 60's, and dangerous defoliation agents were tested at CFB Gagetown from 1956 to 1967. Gagetown tests of Agent Orange and the more toxic Agent Purple in 1966 and 1967 caused a variety of acute and chronic illnesses among soldiers and civilians working there. These tests left Canada with large stockpiles of chemical weapons. Canada eventually abandoned the use of lethal chemical weapons, and had to devote a great deal of effort to safely destroying them. Canada ratified the Chemical Weapons Convention on September 26, 1995. Canada still employs Riot control agents which are classified as chemical weapons.
Canada had a biological warfare research program in the early to middle part of the 20th century. Canadian research involved developing protections against biowarfare attacks and for offensive purposes, often with the help of the UK and the US. Canada has thus experimented with such things as weaponized anthrax, botulinum toxin, ricin, rinderpest virus, Rocky Mountain spotted fever, plague, Brucellosis and tularemia. CFB Suffield is the leading research centre. Canada claims to have destroyed all military stockpiles and to no longer conduct toxin warfare research. Canada ratified the Biological Weapons Convention on September 18, 1972.
Canada maintains a division of its Foreign Affairs department devoted to pursuing these ends. It also dedicates significant resources in trying to verify that current treaties are being obeyed, passing much information on to the United Nations. In the 1970s, Canada discussed building a reconnaissance satellite to monitor adherence to such treaties, but these plans were shelved. A public furor arose in 1983, when the Canadian government approved a plan to test cruise missiles in Alberta.
Canada continues to promote peaceful nuclear technology exemplified by the CANDU reactor. Unlike most designs, the CANDU does not require enriched fuel, and in theory is therefore much less likely to lead to the development of weaponized fissile fuel. However, like all power reactor designs, CANDU reactors produce and use plutonium in their fuel rods during normal operation (roughly 50% of the energy generated in a CANDU reactor comes from the in situ fission of plutonium created in the uranium fuel), and this plutonium could be used in a nuclear explosive if separated and converted to metallic form (albeit only as reactor-grade plutonium, and therefore of limited military usefulness). Accordingly, CANDU reactors, like most power reactors in the world, are subject to safeguards under the United Nations which prevent possible diversion of plutonium. CANDU reactors are designed to be refuelled while running, which makes the details of such safeguards significantly different from other reactor designs. The end result, however, is a consistent and internationally accepted level of proliferation risk.
A common accusation is that India used Canadian reactors to produce plutonium for weapons. India owns two licensed CANDU reactors and began nuclear weapons tests shortly after they became operational in 1972. However, international observers have concluded that no plutonium was diverted from the safeguarded CANDU reactors (see ). The plutonium for the initial bombs came from the older CIRUS reactor built by Canada (see Nuclear Weapons above), but the material for India's most recent nuclear test, Operation Shakti, is thought to come from the locally-designed Dhruva reactor. India has also built a number of reactors, not under IAEA safeguards, that were derived from the CANDU design and are used for power generation. These may also be used for plutonium production.
Canada has volunteered to help destroy some of the leftover chemical weapons of the USSR. There is also talk of taking Soviet nuclear fuel and using it as fuel in CANDU reactors, but this is controversial.
Additionally, Canada is capable of building and maintaining its own nuclear arms should the country desire, owing in part to the extremely high level of scientific ability of the nation and the availability of the required materials, such as uranium, within Canada.