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. 

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 the Canadian 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.

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.