There’s no flashy Oppenheimer cameo, but this scientist helped start the disarmament movement in Canada

Of all the scientists involved in the Manhattan Project, only one walked away from the plan to build a nuclear bomb. But you won't hear the name Joseph Rotblat — or the story of how he brought the fight for nuclear disarmament to a small Nova Scotia village — in Christopher Nolan's hit film Oppenheimer.

Rotblat, a Polish-Jewish physicist, was a member of the British delegation to the top secret U.S.-led mission to develop nuclear weapons known as the Manhattan Project. He left on moral grounds when it became clear that the U.S. would continue to develop an atomic bomb even after Nazi Germany had abandoned its own plans for such a weapon.

Former Canadian Senator and Progressive Conservative MP Douglas Roche, who considered Rotblat a friend and mentor, said he was "eminently courageous" for speaking out against the development of atomic bombs.

Rotblat became a founder of the Pugwash Conferences on Science and World Affairs, named for the picturesque fishing community situated on the Northumberland Strait, where the first meeting was held in July 1957.

The gathering of top nuclear scientists from around the globe aimed to raise awareness about "the catastrophic threat" nuclear weapons posed to humanity. And the work certainly didn't end after one meeting.

Rotblat and the Pugwash Conferences won the Nobel Peace Prize in 1995 for their decades of efforts to eliminate nuclear weapons and diminish their role in politics.

While Oppenheimer might be an entry point to learn about the history of nuclear weapons, advocates like Roche say the Pugwash Conferences should serve as a reminder that there's still much work to do on disarmament.

"It's just far too dangerous for humanity to continue on this path of possessing and expanding, modernizing and developing nuclear weapons," Roche told CBC News, noting that this central message still needs to be heard today as the world observes Hiroshima Day on Aug. 6 and Nagasaki Day on Aug. 9.

The manifesto

In July 1955, a manifesto issued by philosopher Bertrand Russell and physicist Albert Einstein and signed by other leading intellectuals and scientists, including Rotblat, appealed to the world to recognize the perils of the nuclear arms race and to instead seek peaceful resolutions to conflicts.

By this point, the U.S., U.S.S.R. and U.K. were all nuclear armed and the U.S. had completed its test of a much more powerful hydrogen bomb off Bikini Atoll in the Marshall Islands, explained Paul Meyer, the director and former chair of theCanadian Pugwash Group and an international studies professor at Simon Fraser University.

The manifesto, Meyer said, was "a very powerful appeal for some sanity" and a recognition that nuclear weapons, which had already been proven devastating, would likely be deployed in any future wars, so "in order to save humanity" those wars would need to be avoided.

The document called for a politically neutral meeting of scientific minds.

A peaceful place

The village of Pugwash wasn't originally what anyone had in mind when it came to locations for a gathering like the one the manifesto recommended, but options like India and Monaco didn't pan out.

Canadian-American businessman-turned-philanthropist Cyrus Eaton stepped in to help.

Eaton, who was born near Pugwash, owned a property there and offered to cover the costs of hosting Rotblat and 21 other scientists from around the world — including from the Soviet Union and China.

The idyllic and tranquil setting was "part of the success of what transpired" and set the tone for the nuclear disarmament movement, said Sharon Ionno Butcher, the former executive director of the Pugwash Conferences on Science and World Affairs International Secretariat.

"They were able to put aside their concerns being from East and West and different political backgrounds."

According to Ionno Butcher, that first conference and the ones since have "always been about finding that common humanity," bridging divides and developing relationships that allowed the Pugwash Conferences movement to serve as a back-channel intermediary between opposing sides of the Cold War.

The organization also helped lay the groundwork for international agreements such as the Partial Test Ban Treaty in 1963 and the Non-Proliferation Treaty in 1968. Rotblat would serve as the secretary-general of the Pugwash Conferences until 1973.

Eaton's property became known as the Thinkers Lodge and was declared a National Historic Site in 2008. Visitors to the village of Pugwash itself are greeted by a sign proclaiming it "World Famous for Peace."

"There's very few places in the world that you can point to and say 'This is where nuclear disarmament began,' " Ionno Butcher said.

"I just wish that we could say that nuclear disarmament has happened. Unfortunately, we're not there yet."

The nuclear threat today

While you won't see Rotblat portrayed on screen in Oppenheimer, footage of him did appear in The Strangest Dream, a 2008 National Film Board documentary about his life and work.

"I would like everyone to be conscious that they are members of a species which has a marvellous history but whose continued existence can no longer be guaranteed," he said in one clip used in the film.

Roche said his late friend, who died in 2005, would be disappointed by the fact that nuclear tensions have risen again.

"I can hear Rotblat's voice in my mind right now," said Roche. "He would be opposing the insanity of the continuation of the nuclear arms race, which is a race to Armageddon."

Today, nine countries possess more than 12,500 nuclear warheads combined — with six non-nuclear armed nations hosting weapons for other countries — according to the U.S.-based Arms Control Association. Russia has the most warheads, with nearly 6,000, while the U.S. has more than 5,200.

The risk of nuclear warfare did not end with the Cold War and has been revived since Russia invaded Ukraine in February 2022.

Moscow has made threats about using nuclear weapons and has positioned tactical nuclear weapons in neighbouring Belarus.

The Kremlin has also suspended its participation in the New START Nuclear Arms Treaty with the U.S., which allows each country to physically check the other's nuclear arsenal.

Additionally, Russia has accused the U.S. of raising tensions and called on Washington to remove its own nuclear arms from Europe.

That's why Ionno Butcher says the dialogue brought about by the Pugwash Conferences is "more important than ever."

But she would like to see the same level of international co-operation that is now happening to address what she called the "existential threat of global climate change."

"I think sometimes we forget that there's this other existential threat out there that's been there for a very long time."