American invasion of Canada would spark decades-long insurgency, expert predicts

HALIFAX — If U.S. President Donald Trump fails in his stated goal of annexing Canada through economic force, what would happen if he ordered the world’s most powerful military to invade?

Some experts and academics say it’s a notion too preposterous to even contemplate. But Aisha Ahmad isn’t one of them.

“When you look at the power (imbalance) between the U.S. and Canada, an invasion would immediately result in the defeat of the Canadian Armed Forces,” said the University of Toronto political science professor, who last month published an essay on the subject in The Conversation.

“But a conventional military victory is not the end of this story. It’s just the beginning.”

Trump started openly musing about making Canada the 51st state in December, and on Jan. 7 he said the United States might use the military to seize control of Greenland and the Panama Canal. When asked that day if he would use military force to annex Canada, he said: “No, economic force.” The incendiary comments left Canadians wondering just how far Trump would go to achieve such an audacious power grab.

Ahmad, who has studied insurgencies for more than 20 years, says that if the United States were “reckless” enough to invade its northern neighbour, a violent repression of the Canadian population would herald the beginning of a decades-long resistance.

“It’s impossible to annex Canada without violence,” said Ahmad, who has advised generals at the Pentagon about counter-insurgency strategies. “No one is born an insurgent or resistance fighter. This is something that happens to people when their mom is killed, or when their kids are unable to get to a hospital. People fight back because they have to.”

Ahmad said otherwise ordinary citizens would start engaging in mild civil disobedience — cutting wires, diverting funds, thwarting the occupiers in small ways. Others would escalate to sabotage, ambushes and raids, sowing disorder and slowly draining the invading army of its energy and resources. Neighbours would provide the insurgents with safe havens, allowing them to fade back into the population.

“The research on guerrilla wars clearly shows that weaker parties can use unconventional methods to cripple a more powerful enemy over many years,” Ahmad wrote in The Conversation.

“This approach treats waging war as a secret, part-time job that an ordinary person can do …. Trump is delusional if he believes that 40 million Canadians will passively accept conquest.”

If only one per cent of Canada’s population worked to undermine American forces, that would be 400,000 insurgents. That’s about 10 times the number of Taliban fighters who outlasted the American-led coalition during a brutal 20-year war in Afghanistan, Ahmad said. Americans have a poor track record at counter-insurgency, she said, pointing to U.S.-led wars in Iraq, Vietnam and elsewhere.

Howard Coombs, director of the Queen’s Centre for International and Defence Policy in Kingston, Ont., agreed that a successful invasion wouldn’t take long, but he insisted it wouldn’t be particularly violent.

The U.S. military would try to limit the amount of destruction and death to prevent creating a disaffected population, he said. It’s a strategy that showed some success for the American and Canadian militaries during the war in Afghanistan, he added.

“Having a co-operative population or a neutral population is preferable to having a population that would fight you in thousands of small ways,” said Coombs, a graduate of the U.S. Army Command and General Staff College at Fort Leavenworth in Kansas.

“I served with the Americans and I trained with the Americans,” he said. “I spent two years in their system, learning how they fight wars. They don’t need to come in with overwhelming force. I don’t understand why we would think they would.”

Coombs, who retired from full-time duty with the Canadian military in 2003, also challenged the idea that Canadians would be able to mount a prolonged and violent resistance.

“We all like to think in our hearts that we would fight to the bitter end, but I honestly don’t think that would be the case,” he said, adding that the insurgency wouldn’t last long because supplies would quickly run out. “We don’t have a porous border that would allow the shipment of supplies to Canadians …. Is Russia going to ship stuff across Alaska to us? Are we going to get air drops from the U.K.?”

Ahmad argued that Russia and China would be keen to support any conflict that would sap the strength of the world’s most dominant economic and military power. She said the two countries could covertly funnel arms and supplies through proxies. “I have seen this play out in other war theatres, where the sides switch so fast,” Ahmad said.

Meanwhile, American military historian Eliot Cohen said Canadians shouldn’t lose sleep about a U.S. invasion.

“The whole notion is absurd,” said Cohen, a former dean of the Johns Hopkins School of Advanced International Studies in Washington, D.C. “Even this idiotic (U.S.) administration would not dream of doing it.”

Cohen said Trump’s bluster and brow-beating should not be taken seriously. “My advice to my Canadian friends is: Don’t give him the pleasure of getting upset.”

In a recent article published in The Atlantic magazine, Cohen used a tongue-in-cheek approach to warn Americans against invading Canada, pointing out that previous attempts led to dismal results.

His review of American military failures starts in 1775, when U.S. troops invaded Quebec, where they distributed pamphlets — translated into French — awkwardly declaring: “You have been conquered into liberty.” The campaign ended in disastrous defeat for the American Continental Army in December 1775.

During the War of 1812, former U.S. president Thomas Jefferson said conquering Canada was “a mere matter of marching.”

“This was incorrect,” Cohen wrote. “The United States launched eight or nine invasions of Canada during the War of 1812, winning only one fruitless battle. The rest of the time, it got walloped.”

Cohen said he also wanted to remind Americans about the deep sacrifices Canada made during two world wars and in Afghanistan.

“Canada is a gigantic country with 40 million people who really don’t want to be Americans,” Cohen said in an interview. “(An invasion) would be a monumental enterprise. The opposition to it would be across the board in the United States. And who the hell wants 40 million progressives in the United States? It makes no sense.”

This report by The Canadian Press was first published March 30, 2025.

Michael MacDonald, The Canadian Press