But when Prime Minister Justin Trudeau steps down in a few days, his successor will face the worst relations between the U.S. and Canada since the trade war of the Great Depression. Arguably they are nearing a nadir not seen since the 19th century.

After a week of confusing signals from the White House, Mr. Trump said he was committed to imposing potentially devastating 25 percent tariffs on most exports from Canada except oil and gas, which face a 10 percent tax.

[Read: Trump Says Canada and Mexico Tariffs Will Go Into Effect Next Week]

If we recall when Mr. Trump first started proposing tariffs on Canada and Mexico, which now seems a very long time ago, he had two justifications. He insisted that the U.S. was being overrun by migrants and poisoned with fentanyl coming across the borders with the country’s two major trading partners.

Mr. Trudeau’s government responded with a 1.3 billion Canadian dollar package of measures to fortify the border. He named a “fentanyl czar,” gave the Mounties two Black Hawk helicopters to fly along the border, assigned a large number of their officers to border patrol and bought a variety of surveillance devices, including drones.

Matina Stevis-Gridneff, our Canada bureau chief, went to Coutts, Alberta, to see the project in action. What she found is that instead of stopping migrants coming out of Canada, the new patrols are picking up people fleeing from the U.S.

[Read: Canada Curbed Illegal Migration to the U.S. Now People Are Heading to Canada.]

Mr. Trump’s arguments for tariffs are sometimes based around the view that the U.S. is, as he puts it, subsidizing Canada. The idea is part of a general argument by the president that trade is being used by the rest of the world to “rip off” the U.S. and undermine its industries.

In Canada’s case, his subsidy claim appears related to its trade surplus with the U.S. That surplus is largely a result of oil and gas exports to the U.S. Because Americans receive goods and services from Canada for their money, the trade surplus in no way fits the definition of a subsidy.

My colleagues Ana Swanson, Andrew Duehren and Colby Smith write that “Mr. Trump maintains that tariffs will impose few, if any, costs on the United States and rake in huge sums of revenue that the government can use to pay for tax cuts and spending and even to balance the federal budget.”

But in their analysis of Mr. Trump’s trade pronouncements, they found that “tariffs cannot simultaneously achieve all of the goals that Mr. Trump has expressed. In fact, many of his aims contradict and undermine one another.”

[Read: When It Comes to Tariffs, Trump Can’t Have It All]

If a last-minute reprieve doesn’t come and tariffs are in effect just after midnight on Tuesday, Mr. Trudeau has made clear that Canada will retaliate with taxes of its own.

But they are not likely to make Mr. Trump immediately backtrack, nor will they reverse the plant closings or inflation that most experts and many industry leaders anticipate.

A petition is circulating that calls on the government to revoke the Canadian citizenship of Elon Musk, the multibillionaire whose work for Mr. Trump makes him, it says, “a member of a foreign government that is attempting to erase Canadian sovereignty.”

• Norimitsu Onishi has written a sensitive and revealing profile of Sandra Demontigny, a 45-year-old mother of three from Lévis, Quebec, who, after being diagnosed with early-onset Alzheimer’s, pushed the province to become one of the few places in the world to allow people to choose a medically assisted death years in advance.

• Ian Willms, a photographer in Toronto and a regular contributor to The Times, has a powerful visual story of the safe injection site at the city’s Moss Park. Since 2018, it has reversed 3,040 overdoses, Now, a developer is planning to build a condo there. Ontario’s government has said it will stop new safe injection sites from opening, which means this site won’t be allowed a new license to reopen once it’s evicted.

• A search of the Prairie Green Landfill near Winnipeg has “identified potential human remains.” Matina Stevis-Gridneff and Kim Wheeler report that they “could be the remains of two Indigenous women murdered by a serial killer, a possible breakthrough in a case that has devastated local communities and brought to the fore the issue of violence against Indigenous women in Canada.”

• In Books, Leah Greenblatt reviews two “highly personal tributes” to Joni Mitchell.

• Drake has canceled four tour dates in Australia and New Zealand because of what his representatives described as a “scheduling conflict.”

• Josh Ocampo of Times Insider chatted with me about my job.

Ian Austen reports on Canada for The Times and is based in Ottawa. Originally from Windsor, Ontario, he covers politics, culture and the people of Canada and has reported on the country for two decades. He can be reached at austen@nytimes.com. More about Ian Austen

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