In the next few weeks, Prime Minister Mark Carney’s government will make one of the most important decisions of its short life, with enormous consequences for Canada’s relations with the United States and our national defence. That decision is whether to stick with the proposed purchase of eighty-eight F-35 fighter jets.

To grasp what’s at stake, it helps to see how Canada’s military has long conceived of its role. For eighty years, it has understood itself in a particular way. On the surface, it talks about weapons and capabilities. But underneath that jargon lies a guiding doctrine: that Canada’s armed forces belong as close as possible to the side of the US military.

The armed forces even have a word for it: interoperability. In practice, interoperability means building a military designed to work in lockstep with its US counterpart at the highest levels of combat. This is a level of integration far beyond what most North Atlantic Treaty Organization allies seek through such things as standardized stocks of ammunition. The Royal Canadian Navy is one of a very few navies that can seamlessly embed a ship into a US carrier battle group—and has regularly done so. Our army commanders are trained to operate jointly with US counterparts. And the Royal Canadian Air Force functions as part of a broader binational framework of air defence, which is led by the US.

Interoperability with America’s war-fighting ranks is the cornerstone of our approach to defence. You might call it the Canadian military’s world view.

This world view arose during the Cold War, when the idea that Canada would ever act militarily apart from the US was inconceivable. But is this still the case? As US president Donald Trump casts doubt on America’s commitment to NATO’s core principle—Article 5, the pledge that an attack on one is an attack on all—should Canada assume it will always fight alongside the US?

That question is at the heart of Canadian defence planning today—and our acquisition of the F-35. Do we develop capacities that reduce reliance on the US by acquiring the ability to work with others and be more self-reliant? Or do we bet on Trump as a temporary blip, trusting that sanity will be restored, and thus resist throwing away the benefits of decades of close interoperability?

The fight over the fighter jet is where the debate cuts deepest right now. If we opt to purchase the F-35, and no other type of high-tech warplane, we will make a critical aspect of our defence utterly dependent on continued co-operation with the US. Canada’s F-35s will be reliant on the US to be able to function, much more than any previous jet we have purchased has ever been, even ones made in the US, such as the F-18.

The RCAF has been pushing the government to follow through on its contract with the US defence giant Lockheed Martin, which builds the F-35. For the RCAF, it’s a contest between the plane’s strengths and the potential of its rivals. But the decision turns on more than competing hardware. My discussions with retired RCAF generals tend to end on the same plaintive note: if we don’t buy the F-35, we won’t have an air force anymore. This is, of course, absurd. Many countries don’t have F-35s and have perfectly good (and quite lethal) air forces. The countries include France and Sweden, two allies who have eschewed the F-35 in favour of their own aircraft.

What my friends are saying, however, is that if Canada turns away from the F-35, we won’t have an RCAF as they understand it and have trained their whole lives for, one which is seamlessly interoperable with the US Air Force. These are thoroughly good and decent men who have risked their lives to defend Canada. But they simply cannot........

© The Walrus