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Prime Minister Mark Carney speaks about the trade dispute with the United States at the Davie Shipyard in Levis, Que., on Monday.AFP Contributor#AFP/AFP/Getty Images

A trade war can be measured in many ways. The value of goods crossing a border. The percentage rate of tariffs. The number of jobs gained or lost. But victory in the current confrontation with the United States will come down to an intangible: how much do Canadians value their freedom?

The trade terms proposed by the United States were unacceptable. Canada would have been a sovereign country in name but not in fact, its independence an illusion.

As this space argued yesterday, Prime Minister Mark Carney was right to walk away. And he was right to say that U.S. attacks would be countered and struggling Canadians would be helped.

Because there will be pain. Only days after the collapse of trade talks, U.S. President Donald Trump threatened 50-per-cent tariffs on vehicles, auto parts and steel, beginning at the start of next year.

This is a blatant attempt to destroy key parts of the Canadian economy, wiping out thousands of jobs. But it’s more than that. It seeks subservience. It’s the economic equivalent of setting out to bomb a city until its defeated and demoralized leaders seek peace at any cost.

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Mr. Trump clearly wants to enact so much damage that Canadians are begging for relief, willing to accept whatever terms necessary to end the punishment.

The key question now is how much pain are Canadians willing to endure to stay a proud and free country.

Early indications are positive. An Angus Reid poll done over the weekend found strong majority support for Mr. Carney’s trade stance in every province – including among more than half of respondents who voted Conservative in the last federal election.

Mr. Trump should not mistake Canadian politeness for passivity. A country that fought and died in the charnel houses of the world wars, in Korea and in Afghanistan knows the value of standing up for its ideals.

That same poll shows that one in eight people are “very” concerned about losing their jobs and a further 25 per cent are somewhat anxious about that prospect. These fears are legitimate and every lost job is a trauma for that person, with the effects rippling out from there.

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However, Canadians should remain united and clear-eyed about who is at fault. There is only one answer: Mr. Trump. We did not seek this fight. It was Mr. Trump who caused the trade war by seeking to dominate Canada.

By acting so thuggishly, the U.S. administration shot itself in the foot. Mr. Carney might have been able to swallow trade concessions – not an assault on sovereignty. In taking that tack, Mr. Trump clarified that the real issue for Canada is no longer trade, but its survival as an independent country.

In spite of Mr. Trump’s repeated musings about annexing Canada, his primary goal seems to have been simpler: turn Canada into a sort of protectorate.

In this scenario, Canada would not be a part of the United States but not truly independent either. It would be subject to the whims of the U.S. president, unable to set its own foreign or trade policy.

Last year, former prime minister Stephen Harper said that if he were still leader he would accept “any level of damage” to Canada rather than see it absorbed by the United States. “I would be prepared to impoverish the country,” he said.

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That would be a terrible cost. It’s also the right attitude. Freedom, to borrow a phrase, isn’t free.

Given Mr. Trump’s attacks on Canada, it may seem odd to quote here one of his predecessors. But a famous comment from John F. Kennedy’s inaugural address offers inspiration for Canadians. He pledged in 1961 that his country would “pay any price, bear any burden, meet any hardship … to assure the survival and the success of liberty.”

Although Mr. Kennedy was speaking about liberty globally, not specifically in his own country, his is the determination now required of Canadians.

Principles are easy to claim when they are not challenged, when they require no sacrifice. Now Canada is being challenged and sacrifice will be required. The coming period will be hard, the damage may be awful, but no one should ignore what is at stake.

In his dystopian novel A Clockwork Orange, Anthony Burgess has a character who bemoans those who “will sell liberty for a quieter life.” That’s a trade Canadians can never make.