Indeed, submarines are fundamental to the effectiveness of the Canadian navy and the Canadian Forces, and they're essential for sovereignty. There are are couple of reasons for that. If you've been on board I'm sure they gave you a lecture about all of these aspects.
There's a reason that countries, large and small, throughout the Asia-Pacific region are all investing in significant submarine capability. That's in part because the platforms are exceptionally capable at looking after the defence of territorial waters and because China now owns the second largest submarine fleet in the world. More broadly, it's their stealth and lethality that make them the dominant platform at sea for deterrence, for war fighting, and for independent operations, whether that's for intelligence collection or war fighting by themselves.
When I talk about war fighting, you'll remember that the key to this is that it's the deterrence that come with owning those platforms that hopefully means they don't wind up having to be used. But that capability is there, and the key to that capability under stealth is simply that the mere presence or belief that a submarine is in a region is enough to change the operational thinking of adversaries and make them reconsider their plans.
To get to the bottom line of all of this, it's because—and we've all been commanding officers—there is no platform at sea that so worries or creates fear in an adversary's mind as submarines. Now, as to how many, that's an issue of consideration of what the government wishes to accomplish in the future and at what cost. All I will say is that Australia, with a population of two-thirds of ours, currently owns six submarines and is going to replace them with 12 French and Australian-built French submarines. That gives you an indication of how much Australia values the capability. It's partly because of the neighbourhood they live in.