lead
Prime Minister Mark Carney has said the military is running scenarios in the unlikely case the US invades Canada.
Prime Minister Mark Carney admitted last week that he has prepared for a once-unthinkable scenario - a US invasion.
Noting the risk was low and the likelihood highly improbable, he told the New York Times he had a responsibility to consider all possibilities as the US-Canada relationship is redefined under the Donald Trump presidency.
"That's just risk management," Carney said.
In 2025, the US president said it was "highly unlikely" that the US would ever use force against Canada.
"President Trump has done more than anyone to protect the great people of Canada," the White House told the BBC in a statement this week.
Military experts who spoke to the BBC also think an invasion is a long shot, pointing to the multiple ways the two countries work together on defence.
A war between Canada and the US would be complicated and almost difficult to imagine, said Lt-Gen Christopher Coates, a former military officer of 34 years with the Royal Canadian Air Force who held various senior positions.
"I was involved in military operations for my whole career, and we never considered the possibility that there would be a military attack coming from US territory," he told the BBC.
Coates, who had served on Nato missions, noted that Canada and the US collaborate on many aspects of military defence.
Because of this, Coates said he believes an attack by the US on Canada would not begin with an armed assault, but rather with more discreet means like cyberwarfare.
In fact, a core tenet of Canada's identity is its resistance of US expansionism in the 18th and 19th Centuries, said Tim Foran, a researcher with the Canadian War Museum.
Foran said that at the time, the colonies that later became Canada relied on Great Britain and its Royal Navy for its defence, as well as indigenous peoples who served as generals in major battles.
A war was an unlikely scenario then, said Andrew Burtch, a researcher with the Canadian War Museum with expertise on Canada in the 20th Century, but the Canadians still wanted to be prepared.
Even if a US invasion is extremely unlikely, Matthew Schmidt, an associate professor of national security at the University of New Haven in Connecticut, said the fact that Canadians were preparing was a sign of just how drastically the global order has shifted.
According to the model used by the Canadian military, as reported on by the Globe and Mail newspaper earlier this year, a US attack would see Canada's strategic positions overwhelmed within a week
Allied nations like France and Britain would be called on to provide support and defence for Canada, the newspaper reported in January, citing senior government officials.
The modelling is on the lighter end of military combat planning, Coates said.
Even with its outsized military, the US would have a difficult time getting buy-in for a fight with Canada, said Schmidt.
Schmidt said Canadian soldiers and American soldiers routinely train together, and share a mutual respect.
But in the unlikely scenario that relations would deteriorate to the point of combat, Schmidt said the US would likely focus on acquiring valuable Canadian resources like oil and minerals, and political decapitation.