We've all heard the cliched phrases: The Silent Service. Run silent, run deep. But the reality is that every year or two an incident involving one of the submarines of the world's navies will make the news. The latest such incident is a "one in a million" collision between the HMS Vanguard of the Royal Navy of the United Kingdom, and the French Nav's Le Triomphant earlier this month. Both boats survived, but the Vanguard had to be towed back to port. What is sure to keep this story in the news a bit longer than some other collisions is that both boats were SSBNs, nuclear subs carrying nuclear armed ballistic missiles. These subs play the same role in the British and French navies as they do in those of the United States and Russia, the ultimate deterent against nuclear attack. Both subs carry a compliment of 16 submarine launched ballistic missiles, American made D5 Tridents on the Vanguard, French made M45s on Le Triomphant.
It's sobering to consider the destructive power a single one of these vessels carries. It's unclear how many warheads either sub carries on each of its missiles these days, but 3 is the general assumption for Vanguard. Therefore 6 missiles would be sufficient to hit every city in Canada with a population of 100 thousand people or more. And it is this firepower that is the rationale behind these subs, for it sends the message to any potential nuclear armed foe that any nuclear attack will result in the destruction of their country from a source they would be unable to detect in time to prevent retaliation, should they even have the capability to do so. Both nations keep one of these vessels at sea at all times.
SSBN's are designed to be as hard to detect as is practical, and this quite obviously played a role in the collision. Neither boat heard each other, and of course neither was supposed to know where the other was. The exact patrol routes for such subs are closely guarded secrets, since enemies not knowing where to hunt for them is part of their operational goal. So any sort of calls for somehow coordinating operations to prevent such a collision are likely to be ignored.