MONTREAL — One was a self-fashioned fixer in North Korea who had met that country’s enigmatic leader, Kim Jong-un, and drank Long Island iced teas with him on his private yacht.

The other was an experienced diplomat and Sinophile who had spent years investigating sensitive subjects like the human rights of minority groups in China.

Both the entrepreneur, Michael Spavor, and the former diplomat, Michael Kovrig, have been detained in China, after spending decades living and working in authoritarian states. Now, they have found themselves in the center of a perilous geopolitical battle, Canadian pawns in a larger contest between two of the world’s biggest superpowers, China and the United States.

On Friday, Prime Minister Justin Trudeau of Canada said their detainment was unacceptable, and warned that Canada was getting ensnared in a dust-up between the United States and China.