What is the strategic importance of submarine-launched ballistic missiles?
Imagine a nation in possession of nuclear weapons & absence of No first use (NFU) policy comes in war with any other nation & completely loses that war. Their military backbone is broken & they are facing an acute embarrassment. Their last resort to revenge is launching a nuclear attack. These attacks don’t need foot soldiers or tanks or logistical support. The ballistic missiles can be launched in a feeling of revenge in a couple of minutes, from a remote underground location. These missiles would target high density civilian crowded cities. This is called First Strike & is the last resort of any nation in case it is on the verge of losing a war.
Now understand that starting a Nuclear war is the path for what is called Mutual Assured Destruction. It is a doctrine of a full scale use of Nuclear weapons which will cause a full scale annihilation of both the attacker & the defender. The answer of a Nuclear Missile strike is another Nuclear Missile. After the losing nation attacks, the “First use” has been done & the No first use (NFU) policy, even if it is signed by the other nation, gets void & they also start launching their Nuclear tipped ballistic missiles. Both sides are in a state of Nuclear war until total annihilation. This is called Mutual Assured Destruction.
Now here comes the role of Ballistic missile Submarines.
If you have even one Ballistic Missile Submarine (SSBN) that has multiple ballistic nuclear missiles, the enemy knows that even if all your airbases & ballistic missile silos on land (by which you could do a retaliatory nuclear strike) are destroyed, you can still strike back at the enemy from anywhere, undetected, like a ghost. The enemy knows that there is a Nuclear missile equipped submarine somewhere out there, hidden in the ocean that they can never find. This way a country can carry out a effective nuclear strike even after absorbing a nuclear attack.
SSBNs can stay underwater for extremely long periods of time & can cover huge distances by staying undetected. Usually SSBNs have enough firepower to completely obliterate a big nation. They can slowly creep in very near to the enemy by travelling under the water & can launch all its Nuclear missiles in one go & can wipe out an entire country. You just cannot stop them.
This is called fear & this fear causes deterrence in the hearts of enemy to never use a Nuclear missile.
It is thus of utmost importance that the Ballistic missile submarines always remain hidden & undetected. Their exact route is secret & is known to only few with the highest level of security clearance in the Navy. Like in our case, nobody in India (except for a handful of people) knows where in the world is INS Arihant (pic below ) sailing right now.
The best way to prevent a first strike (from enemy) is having a covert & powerful second strike (from the defender).
Letters of Last Resort:
In UK, this is a handwritten letter from the Prime Minister to the four Nuclear ballistic missile submarines. They contain orders on what actions to take in case of a nuclear strike that would completely destroy the Great Britain. This letter is kept in a safe inside the ballistic missile submarine & the letter is meant to be read only when there is complete annihilation of the United Kingdom.
One of these 4 options are written by the PM to the Sub commander:
- Retaliate with Nuclear weapons
- Don’t retaliate
- Use your own judgement
- Place the submarine in an allied country’s command.
- The letter is destroyed without reading after the PM leaves the Office & new letter is issued by the new PM which are transferred to the submarine in a sealed container at the earliest.
These if ever executed will be the last official orders of the Government of UK.