When I served as counselor of the State Department, I advised the secretary of state about America’s wars with Iraqi insurgents, the Taliban, Iran’s Islamic Revolutionary Guard Corps, and al-Qaeda. I spent a good deal of time visiting battlefields in the Middle East and Afghanistan as well as shaping strategy in Washington. But when I left government service in 2009, I eagerly resumed work on a book that dealt with America’s most durable, and in many ways most effective and important, enemy: Canada.

So I feel both morally compelled and professionally qualified to examine the Trump administration’s interesting but far from original idea of absorbing that country into the union.

There are, as Donald Trump and Don Corleone might put it, two ways of doing this: the easy way and the hard way. The easy way would be if Canadians rose up en masse clamoring to join the United States. Even so, there would be awkwardness.

[Read: The angry Canadian]

Canada is slightly larger than America. That would mean that the “cherished 51st state,” as Trump calls it, would be lopsided in terms of territory. It would be 23 times larger than California, which would be fine for owning the libs, but it would also be 14 times larger than the Lone Star State, which would definitely cause some pursed lips and steely looks there. Messing with Texas is a bad idea.

The new state would be the largest in population too, with 40 million people—more than California by a hair, and considerably more than Texas, Florida, or New York. Its size would pose a whole bunch of problems for Trump: Canada is a much more left-wing country than the United States, and absorbing it could well revive the political fortunes of progressives. If its 10 provinces became 10 states instead of one, only three would probably vote for the GOP; the other seven would likely go for Democrats. That might mean adding six Republican senators and 14 Democrats. If Trump were impeached a third time, that might produce the supermajority required for conviction in the Senate.

But such political ramifications are purely academic considerations at the moment. Polling suggests that 85 to 90 percent of all Canadians cling to sovereignty. Having been denied the easy way of absorbing Canada, therefore, the United States might have to try the hard way, conquering the country and administering it as a territory until it is purged of Liberals, Conservatives, and whatever the Canadian equivalent of RINOs turns out to be.

Unfortunately, we have tried this before, with dismal results. In 1775, before the United States had even formally declared independence from Great Britain, it launched an invasion of Canada, hoping to make it the 14th colony. The psychological-warfare geniuses in Congress ordered that the local farmers and villagers be distributed pamphlets—translated into French—declaring, “You have been conquered into liberty,” an interesting way of putting it. Unfortunately, the Catholic farmers and villagers were largely illiterate, and their leaders, the gentry and parish priests who could read, were solidly on the side of the British against a bunch of invading Protestants.

There were moments of brilliant leadership in this invasion, particularly in a daring autumn march through Maine to the very walls of Quebec. There was also a great deal of poltroonery and bungling. The Americans had three talented generals. The first, Richard Montgomery, got killed in the opening assault on Quebec. The second, John Thomas, died of smallpox, along with many of his men. Inoculation was possible, but, like today’s vaccine skeptics, many thought it a bad idea. You can visit the capacious cemetery for the victims on Île aux Noix, now Fort Lennox, Canada.

The third general, the most talented of the lot, was Benedict Arnold, who held the expedition together even after suffering a grievous leg wound. Eventually, however, he grew disgusted with a Congress rather less craven and incompetent than its contemporary successor and became a traitor, accepting a commission as a brigadier general in the British army and fighting against American forces.

We tried again in 1812. Thomas Jefferson, the original Republican, described the acquisition of Canada as “a mere matter of marching.” This was incorrect. 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. For example, General William Hull, like other American commanders a superannuated veteran of the Revolution, ended up surrendering Detroit with 2,500 troops to a much smaller British and Indian force. Court-martialed for cowardice and neglect of duty in 1814, he was sentenced to death but pardoned.

Secretary of Defense Pete Hegseth is perhaps unfamiliar with the Battle of Chateaugay. The last three letters are, after all, gay, and as such, the battle has doubtless been expunged from Defense Department websites and databases, meeting the same fate as the Enola Gay. Still, it is instructive. An invading force of 2,600 American regulars encountered about 1,500 Canadian militia members, volunteers, and Mohawks under a Francophone colonel, Charles de Salaberry.  They were defeated and had to withdraw.

Since the War of 1812, Americans have not tried any formal invasions of Canada, but there was tacit and sometimes overt support for the 1837–38 revolt of the Canadian patriotes, a confrontation over Oregon (a sober look at the size of the Royal Navy dissuaded us from trying anything), and the Fenian raids of 1866 and 1870. The Fenians were rather like the Proud Boys, only better organized and all Irish, and they also ended up fleeing back over the border.

Perhaps today’s Canadians are a flimsier lot. The Canadian armed forces are quite small (the army numbers only about 42,000, including reservists), although spirited and hardy. One should note with respect that 158 Canadians were killed fighting alongside American soldiers in Afghanistan. But even if the Canadian military were overcome after some initial bloody battles, what then?

Canadians may have gone in for wokeness in recent years, it is true, but there is the matter of their bloody-minded DNA. It was not that long ago that they harvested baby seals—the ones with the big, sad, adorable brown eyes—with short iron clubs. They love hockey, a sport that would have pleased the emperors and blood-crazed plebeians and patricians of ancient Rome if they could only have figured out how to build an ice rink in the Colosseum.

[Read: Canada is taking Trump seriously and personally]

Parenthetically, there remains the problem of the First Nations (as the Canadians refer to them), whom they treated somewhat less badly than Americans treated Native Americans (as we refer to them). There are about 50,000 Mohawks straddling the U.S.-Canadian border, and they are fearless, which is why you will find them building skyscrapers at terrifying heights above the street. As members of what used to be the Iroquois Confederacy, they were ferocious warriors, and they retain a martial tradition. It is sobering to consider that they may think, with reason, that we are the illegal immigrants who have ruined the country, and therefore hold a grudge.

There is a martial spirit up north waiting to be reawakened. Members of the Trump administration may not have heard of Vimy Ridge, Dieppe, the crossing of the Sangro, Juno Beach, or the Battle of the Scheldt. Take it from a military historian: The Canadian soldiers were formidable, as were the sailors who escorted convoys across the North Atlantic and the airmen who flew in the Battle of Britain and the air war over Germany. Canada’s 44,000 dead represented a higher percentage of the population than America’s losses in the Second World War. Those who served were almost entirely volunteers.

Bottom line: It is not a good idea to invade Canada. I recommend that in order to avoid the Trump administration becoming even more of a laughingstock, Secretary Hegseth find, read, and distribute to the White House a good account of the Battle of Chateau***. It could help avoid embarrassment.

The Founders knew that Americans, for better or worse, had an insatiable desire for overseas trade. “They are as aquatic as the tortoises and sea-fowl,” observed John Adams, “and the love of commerce, with its conveniences and pleasures, is a habit in them as unalterable as their natures.” As early as 1785 he foresaw that Americans would be compelled to form “connections with Europe, Asia, and Africa,” and he advised that “the sooner we form those connections into a judicious system, the better it will be for us and our children.” Thomas Jefferson would have preferred to cease all commerce with the rest of the world and rely on the simple virtues of the “yeoman farmer,” but he knew this was impossible. “Our people have a decided taste for navigation and commerce … and their servants are in duty bound to calculate all their measures on this datum.” Even that much-caricatured “Jacksonian,” Andrew Jackson himself, as president never fired a shot in anger but negotiated more trade agreements with foreign powers than any of his predecessors.

The American love of trade made using the practice as a weapon against other nations difficult. When Jefferson forgot his own lesson and tried to embargo trade with Great Britain in 1807 in response to the British navy’s abuse of American merchants on the high seas, his efforts backfired, stirring talk of secession in the New England states that conducted most of that trade. It turned out to be easier to get Americans to support a shooting war with Great Britain than a trade war.

Donald Trump is now learning the hard way how vulnerable America is when it comes to trade wars. This is not because the United States doesn’t in theory hold the strongest hand. The American market is the most desired in the world, and any restriction on access to that market should hurt other countries more than it hurts the United States. The ratio of international trade to GDP for the U.S. is roughly 25 percent, compared with more than 60 percent on average for all other nations. In Germany, foreign trade tallies up to 90 percent of GDP. That ought to make the country vulnerable and give the United States leverage. In practice, however, Americans have proved time and again that they have a very low threshold of pain when it comes to trade wars. Jefferson was not wrong to believe that Britain depended heavily on American trade when he launched his embargo in 1807; what he did not anticipate was that his own citizens would cave before Britain did.

[Read: How Republicans learned to love high prices]

The problem is, or at least has been up until now, democracy, and, more specifically, electoral politics in a federal system where narrow, local interests can have broad national political impact. A trade dispute might harm only one sector of the economy, but if that sector happens to coincide with a crucial voting bloc, it can put the United States at a disadvantage in a contest with a nominally weaker power.

A good example of this came during World War I, before the United States had entered the war and Woodrow Wilson was trying to navigate his way through British blockades and German submarine attacks on transatlantic shipping while desperately trying to preserve American neutrality. The United States was far less reliant on international trade then; it was only 11 percent of GDP. But as Wilson learned, even damage to particular sectors of the economy could threaten political upheaval. Although his personal inclinations were pro-British, for instance, London’s threats to blockade cotton as contraband of war infuriated the Democrats’ key southern constituency. Wilson’s secretary of the Treasury, William Gibbs McAdoo, recalled spending “more sleepless nights thinking about cotton” than about anything else during his time in office. The rest of his sleepless nights were spent worrying about finding markets for midwestern grain, much of which had been purchased by Germany and other European nations prior to the war. These specific sectors, because they involved states and regions essential to national political coalitions, had influence on American decision making that exceeded their overall importance to the American economy.  

[Read: Trump’s most inexplicable decision yet]

Trump must believe, as Jefferson did, that the world needs America more than America needs the world, and he may be right—in theory. The problem is that individual voting blocs mean more to him than carrying out a consistent trade war, as he has repeatedly demonstrated during both terms in office. In his first term, the damage done to farmers by his tariffs on imports was sufficiently threatening politically that he had to spend much of the money gained by the tariffs to compensate the farmers for their losses. His vacillations and emendations in his latest rounds of tariffs this year have been similarly motivated by his desire not to alienate Republican voters in particular states—northern-tier states that rely heavily on trade with Canada and automaking states that stand to lose badly from tariffs on auto parts, steel, and aluminum crossing the Mexican and Canadian borders. It is no accident that among the Europeans’ first retaliatory tariffs have been those against Harley-Davidson and American whiskey. Other nations may know their history better than Trump does and have figured out that tariffing sectors of the economy that hit Trump voters can have an impact beyond their dollar value. The United States is a nation split down the middle politically, so marginal voting groups can have a huge effect. This significantly vitiates the American advantage.

It would be one thing if Trump’s supporters were willing to suffer economic hardship in order to show their support for the MAGA way. As Senator Tommy Tuberville of Alabama put it, “There’s going to be some pain with tariffs,” but “no pain, no gain.” The problem for Trump is that, so far, as in the past, even his own voters don’t have much tolerance for pain.