After President Trump imposed tariffs on Canada on Tuesday, Prime Minister Justin Trudeau made an extraordinary statement that was largely lost in the fray of the moment.

“The excuse that he’s giving for these tariffs today of fentanyl is completely bogus, completely unjustified, completely false,” Mr. Trudeau told the news media in Ottawa.

“What he wants is to see a total collapse of the Canadian economy, because that’ll make it easier to annex us,” he added.

This is the story of how Mr. Trudeau went from thinking Mr. Trump was joking when he referred to him as “governor” and Canada as “the 51st state” in early December to publicly stating that Canada’s closest ally and neighbor was implementing a strategy of crushing the country in order to take it over.

The February Calls

Mr. Trump and Mr. Trudeau spoke twice on Feb. 3, once in the morning and again in the afternoon, as part of discussions to stave off tariffs on Canadian exports.

But those early February calls were not just about tariffs.

The details of the conversations between the two leaders, and subsequent discussions among top U.S. and Canadian officials, have not been previously fully reported, and were shared with The New York Times on condition of anonymity by four people with firsthand knowledge of their content. They did not want to be publicly identified discussing a sensitive topic.