The next technical development Golden Dome advocates point to is the advent of large, cost-effective constellations of satellites. The private sector has led this charge, with companies such as Starlink launching thousands of assets which orbit the world in previously impossible arrays. Supporters argue a new network of sensors and space-based interceptors that can stop incoming missiles at their most vulnerable point—the boost phase—is now possible.

But while these private networks are impressive, they are a fraction of what would be required for BMD. Also, little discussed is the fact that placing key components of the system on Low Earth Orbit satellites makes them obvious targets. This sets the stage for a conflict in which tens of thousands of spacecraft could be attacked by equal numbers of weapons designed to blind them with electromagnetic pulses or destroy them through collision.

The result would be a scenario known as the Kessler Syndrome, in which the debris of countless smashed satellites circles Earth in waves and renders access to space impossible for generations.

SO WHAT DOES CANADA do with Trump’s Golden Dome invitation? Both previous times, with Reagan and Bush, Canada’s military wanted to join (there has never been a large US defence project that Canada’s military was not keen to join), but public opinion and other officials were reluctant.

Reagan’s invitation for Canada to participate in the SDI created a dilemma for then prime minister Brian Mulroney. Simply dismissing SDI would not do, even if it would suck up billions and was widely disliked by Canadians. Mulroney’s solution was to decline but refrain from criticizing the initiative while permitting Canadian companies and researchers to take part if asked by the US. It allowed him to say no without offending Reagan. More importantly, it showed Canadians that Mulroney could turn away the US, which protected him from charges that his real ambition—a free trade agreement—smacked of a desire to “sell out” Canadian sovereignty.

A few decades later, the debate in Canada over George W. Bush’s more limited missile-defence plan—called Ground-based Midcourse Defence (GMD)—was fierce. Opponents in the arms control world and at Canada’s Foreign Affairs Department (now Global Affairs Canada), argued that any missile defence would undermine the spirit of strategic stability. The Canadian military countered that Bush’s plan was different from Reagan’s, as it would only stop a handful of incoming missiles—enough to defend against a limited or accidental launch but far too little to counter a large-scale attack by a nuclear power like Russia. Because it could not negate a full retaliatory strike, they argued, it posed no threat to MAD.

Others warned that saying no to Bush could put NORAD at risk. The US might respond by pulling missile tracking out of the binational command. If that happened, it was hard to see what role NORAD would have left.

In the end, the decision taken by then prime minister Paul Martin was political, as both Bush and GMD were unpopular in key Liberal constituencies. But even here, Martin pursued a “no—but” policy. To preserve NORAD, a compromise was fashioned. NORAD provides a critical part of the missile tracking for the Bush-era system, with Canada involved in that stage. But once a decision to launch the interceptor missiles is made, Canadians step back, and control becomes entirely American. As the US ambassador to Canada at the time put it, “We have this odd situation where the Canadians will participate at NORAD, detecting when the missile is launched, determining where it’s heading, and even if they determine it’s heading towards Canada, it’s at that point they’ll have to leave the room because they’re not participating.”

These previous cases matter for understanding Canada’s response to the Golden Dome. In each instance, Ottawa declined to join while taking care not to offend Washington—preserving NORAD and leaving options open. Would that kind of partial agreement work with Trump?

Publicly, aside from the sum Trump wants for membership in his new club, he has not outlined any specific role for Canada. But Canada’s military has effectively been preparing for participation in some aspect of missile defence. Much of this effort centres on an ongoing project to modernize NORAD. In 2022, Canada committed $40 billion to these efforts, including a new Arctic over-the-horizon radar to spot threats far beyond the line of sight.

The focus is on upgrading the sensors needed to detect and track modern ballistic and cruise missiles. NORAD may not have a formal mandate to shoot those missiles down, but improved tracking makes that job easier for those who do. Although this modernization began before the Golden Dome project, missile defence now sits at its centre. Canada has also committed itself to something called Integrated Air and Missile Defence, an approach that dissolves the old boundary between those two domains. The new River-class warships (the navy envisages fifteen in total) have been redesigned around American radar systems that allow them to operate as part of a single, shared architecture. The ships can connect to each other and to American ships such that the commander of one vessel, Canadian or American, can order the firing of missiles from others. Within that framework, the American F-35 fighter jet—of which Canada has committed to at least sixteen—matters less as an aircraft than as a flying sensor and data node, designed to link with other platforms at sea and in space.

Put Canada’s networked warships and F-35s together with their American counterparts, place them under command-and-control systems which make Canadian and US assets essentially the same, throw in a modernized NORAD, add the enhanced US ground-based interceptors and the space-based equivalents planned for the Golden Dome, and you have the very definition of a far-reaching missile-defence system: a tightly meshed, seamless web of tracking and strike capabilities coordinating in real time.

Back in 2023, the Canadian government stated that it had made no decision about taking part in US-led missile defence. Anyone examining the kinds of weapons we are buying, the command systems for them, and the operational concepts we have committed to might wonder differently.

AMERICA’S DREAM OF protecting itself from nuclear attack isn’t going away. Defence of the sacred homeland is too deeply embedded in the US psyche, and its military-industrial complex has too much invested to let the idea go. A perfect missile defence may never be achieved, but the ongoing search for one is endlessly profitable.

But we should also acknowledge the world is no longer what it was in the 1970s, when MAD underpinned the nuclear order and its two actors, the Soviet Union and America, were fundamentally risk averse. China is a new and different player. Vladimir Putin’s Russia seeks to redraw boundaries and is prepared to threaten Armageddon to do it. Recent entrants in the club—such as North Korea and perhaps Iran one day—possess, or soon might, missiles that can reach North America. Against that backdrop, insisting that 1970s-style MAD is the basis of deterrence doesn’t make much sense, and hasn’t for a long time. Limited missile defences may be justified against small-scale threats, even if larger systems remain destabilizing against others.