It’s the last trip that Justin Trudeau never took.

In his last weeks in power, amid the turmoil of Donald Trump’s tariff threats and jibes about making Canada the 51st state, Mr. Trudeau was quietly planning a symbolic and potentially controversial trip to Syria.

The advance teams had been there. Canadian Armed Forces troops were on the ground in Syria preparing to provide security for the prime minister. The date was set for March 1, then cancelled, and another suggested before it was rescheduled for March 7, but cancelled again.

After that it was too late.

The national psychodrama of Mr. Trump’s trade war, in the week before a new Liberal leader was chosen, meant Mr. Trudeau couldn’t go on a mission to the Middle East. His time as prime minister had run out.

It wasn’t just another trip. A visit by the Canadian prime minister to meet with the interim government that had replaced Bashar al-Assad’s regime would have been a significant symbol.

No other Western leader had yet travelled to Syria to shake hands with President Ahmed al-Sharaa. Mr. Trudeau’s planned visit was intended to offer hope that Syria could reintegrate with the world, but travelling to the still-fractious country to meet the leader of a regime based on the Islamist Hay’at Tahrir al-Sham militant group was also a risky venture. It was not at all clear what the transitional government might become.

The prime minister’s advisers knew there might be criticism at home that he was too quick to lay hands on a still largely unknown Islamist government – that after a few months, events in a country still riven by sectarianism might make it look like a bad risk.

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But Mr. Trudeau wanted to go. In his eyes, it was a moment when it might be possible to encourage the interim government, and Syrian actors, toward moderation and pluralism and stability. The foreign affairs ministers of Germany and France had visited Damascus in January, and the U.S. and European Union had begun to suspend some of their economic sanctions.

And reaching out to the Syrians caught in a civil war had been a cause of Mr. Trudeau’s first days in power.

He had promised during the 2015 election campaign – amid heart-rending images of adults and children fleeing Syria’s Civil War – that Canada would resettle 25,000 Syrian refugees. Making that happen was a major challenge for his new government. Eventually, planeloads of Syrians were warmly greeted by Canadians. Mr. Trudeau’s tenure had a connection to Syria. Now there was another moment.

But that was obviously not the highest priority in Canada’s foreign policy. Foreign Affairs Minister Mélanie Joly was mostly grappling with the Trump administration and its trade threats, as well as Ukraine. Mr. Trudeau appointed Syrian-born Mississauga MP Omar Alghabra as a special envoy for Syria, who travelled twice to the Middle East, in January and late February, to meet with senior officials there.

The idea of Mr. Trudeau going himself emerged as the then-prime minister discussed encouraging Syria to stability with other leaders in January and February, including the President of France, the Prime Minister of Italy, the Emir of Qatar and the King of Jordan. France’s Emmanuel Macron invited Mr. al-Sharaa to visit the Élysée Palace in Paris. Mr. Trudeau put Syria on the agenda for Canada’s chairing of the G7.

Western countries were lifting some economic sanctions, and Canada was about to follow suit. In Mr. Trudeau’s office, there was hope that a visit to Damascus could demonstrate that pluralism and stability could lead to a better life for Syrians.

The trip was set for March 1. But that was the weekend before Mr. Trump was set to impose 25-per-cent tariffs on imports from Canada. And Mr. Trudeau was going to London on March 2 for a conference on Ukraine. His officials sought to reschedule the trip for March 6; the Syrians suggested March 7.

But on March 5, Canadians were pulling U.S. alcohol off liquor-store shelves in protest of new U.S. tariffs. On March 6, Mr. Trudeau and his aides were waiting for the partial climb-down that Mr. Trump had signalled, then worked into the evening to figure out the details.

Mr. Trudeau’s last trip, with its symbolism for Syria, and for the outgoing prime minister, was off.