Max Beerbohm said that history doesn’t repeat itself but historians repeat each other. I wonder if the latter repetition doesn’t give rise to the former. Those lucky baby boomers who, like me, have managed to make it past the half-century mark will, in looking back at their college-age revolutionism, have grown used to a sense of déja-vu in hearing the revolutionary rhetoric of the so-called “millennial” generation, particularly when it comes to matters of war and peace. Justin Trudeau, born on Christmas Day, 1971, is no millennial, but he showed that he knows how to use the language of protest from the period of his birth. When asked in an interview about Iran’s shooting down of a Ukrainian passenger jet with fifty-seven Canadians on board, he said, “I think if there were no tensions, if there was no escalation recently in the region, those Canadians would be right now home with their families.”

Unlike me, the Canadian Prime Minister is too young to remember how that word “escalation” came into our political vocabulary and so presumably doesn’t know that its modern usage was invented (or appropriated) by the anti-war Left to redistribute blame from the aggressor to whoever responds to aggression. The great irony of the term is that it was originally part of the jargon of the foreign policy establishment whose conduct in the war in Vietnam had given rise both to the protests and to the defeat that followed on their heels.

To Defense Secretary Robert McNamara and his whiz kids, the ideas of escalation and de-escalation were products of their own innovative genius, a way of conducting war in a new and more up-to-date way than that which had brought about our last true victory in war, in 1945. Their method was to escalate with “measured” force, not to defeat but to punish the enemy and warn him of worse things to come if he persisted in his aggression. Then, so the theory went, when he heeded the warning and de-escalated himself, we could reward him by de-escalating in our turn. Except that, in Vietnam, he never did respond by de-escalating, with the result that the escalator only went, with agonizing slowness, in one direction and so failed completely to achieve its purpose.

Worse than that, the method put the enemy on notice that we had no intention of winning the war, only of pounding him until he did what we wanted. If he declined to do what we wanted, therefore, he knew he only had to wait until we grew tired of pounding him (and being pounded back) for us to go home, leaving him in possession of the field. And so it proved. It was the original rope-a-dope strategy later made famous by Muhammad Ali. Meanwhile, back at home, when it grew obvious to everybody but the generals that the escalator strategy wasn’t working as advertised, “escalation” became a dirty word and therefore a useful one to the Left, which could apply it to any act of violence of which they disapproved, whether or not it was part of an escalator strategy. Indeed, many of those who are criticizing the president are doing so both on account of the alleged escalation and on that of its not conforming to the strategy of escalation — which, as we’ve seen, doesn’t work.

Drained thus of all substantive meaning, the word has a further usefulness to the anti-war party. By applying it to some acts of war but not others, you can pretend to know their result before it happens — always the surest way to make sure you stay on “the right side of history.” Thus, what President Bush called the “surge” of American troops sent in to deal with the Iraqi insurgency in 2007 was called an “escalation” by its Democratic opponents — including then-Senator Obama, who sponsored S.433 or the “Iraq War De-Escalation Act of 2007.” But when that supposed escalation appeared actually to have succeeded in pacifying the insurgency, it could quietly go back to being called the “surge” again, leaving “escalation” to describe the next war-like act to be reflexively opposed.

Mr. Trudeau wishes to gain political points with his left-leaning constituency by suggesting that Mr. Trump should bear the blame for what happened to those Canadians, rather than the people who actually killed them, but he doesn’t dare to come right out and say so. He has recourse instead to this hoary old left-wing cliché to say it for him, but indirectly. It’s a typically passive-aggressive attack on the hated Orange Man on behalf of the international Left — which the media choose to report as the moderate and sober reproach of a genuinely injured party. But what lies behind this abuse of language is a cultural shift that also arose out of the Vietnam War.

Following the well-trodden path of the pacifists of the 1920s and 1930s, who sold the Congress of the day on the Kellogg-Briand pact purporting to “outlaw” war, the anti-warriors of the 1960s and 1970s adopted as their own the assumption that wars are caused not by aggressors but by those who respond to aggression in kind. It was these responders who were deemed to be guilty of perpetuating “the cycle of violence,” which would obviously not exist if they had simply declined to be provoked into a response by any injury, however grievous.

To the honor culture that existed in most Western countries before the First World War and again, in much-diminished form, after the Second, this idea would have been considered plainly insane. The last gasp of that old culture came during the Korean War (1950–53) when Douglas MacArthur, the general leading the United Nations troops against the North Korean and Chinese enemy, said: “In war, there is no substitute for victory.” He was fired for that opinion, and his reputation unjustly blackened by those who went on to invent the sort of escalator warfare that MacArthur was warning against. Sooner or later, but obviously not yet, we’re going to have to acknowledge that they were wrong and MacArthur was right.