I have to go back in history, I think, to differentiate what could constitute a threat to the United States and perhaps not to Canada, and vice versa.
In 1957 when NORAD was formed, there was an implicit recognition of the fact that as far as air defence was considered, it was better to deliver air defence with a continental point of view. This is how both nations joined forces and started to defend our air responsibility with the capability of a conventional air defence system of that time.
As we move through history—and maybe I'll go back to that later—the initial threat was Soviet long-range aircraft with gravity bombs. I might talk about how we defended against those later. Afterwards, we had ballistic missiles, the ICBMs that showed up, which became a threat to North America. Afterwards, we still had the long-range aviation with the first generation of cruise missiles. Now what we see is a new generation of cruise missiles, with very long-range and low observability, which are really challenging our way to prosecute, if you want, any approaches to North America.
From my perspective, it's very difficult to isolate a threat to the United States from a threat to Canada, and vice versa. If we talk about the cruise missiles, the advanced long-range cruise missiles that we have observed are not only still a threat in the aerospace domain but also in the maritime domain, because they are now being launched from submarines and surface vessels. So the maritime domain now is becoming a domain of interest that is really challenging us to think in terms of continental defence, as opposed to only from a perspective of U.S. or Canadian defence. So there I would say it's a common concern.
Ballistic missiles have been around for a long time, including short-range and medium-range ones. There are a lot of technical advances out there in the world. They are here to stay. The intercontinental ballistic missiles are the ones that we see. If you look at the latest manifestation of developments out of North Korea, the truth of the matter is that country is working very hard to develop this capability, despite its missile test last week being a failure.
With respect to the ballistic missiles themselves, it is very difficult for me to imagine that a single shot that hit a U.S. city, for example, Seattle, would not have any implications for Canadian sovereignty, the Canadian economy, and survivability. Even the threat itself, I find difficult to separate as far as being a U.S. threat only or a Canadian threat only.