'Iranian Ship Was A Sitting Duck'

'Torpedoes travel at more than 100 kilometres per hour, about 50-60 knots.'
'It must have been a matter of a few minutes before it detonated under the Iranian ship.'
'The Iranian ship would have probably got three, four minutes and wouldn't have known till they actually heard the whirr of the torpedo.'

"It would be quite a task for even powerful countries like the US to detect, say, every Chinese, Russian or Indian submarine in the Indian Ocean. Oceans are extremely opaque and detecting a nuclear submarine requires tremendous sophisticated resources," says Commodore Srikant Kesnur, retired, who has captained two frontline ships -- an anti-submarine frigate INS Vindhyagiri and India's biggest amphibious ship INS Jalashwa.

"For a country with limited resources -- such as Iran -- the probability of detecting and identifying a nuclear submarine is likely to have been low. If the submarine was detected at all, it may have been too late -- much like a classic jungle ambush where the target realises the threat only when escape is no longer possible," Commodore Kesnur tells Rediff's Archana Masih in a detailed interview discussing the 'hunt and kill' operation that sank the Iranian warship IRIS Dena off the coast of Sri Lanka last week.

According to reports, the Iranian warship was almost stationary and waiting offshore when attacked by the US nuclear submarine. Would that be a correct assumption?

It is a misnomer to say that the warship was 'almost stationary' because ships are never 'almost stationary'.

That may be the perspective from the images released by the US submarine. At times, a submarine aligns her speed with that of a surface ship which makes it appear to be stationary. But in reality, it is still in motion.

There are reports that the ship was waiting outside Galle seeking entry.

While I cannot speculate on that, but if true it does not change what I said. Even when waiting outside a port, they are not stationary or at zero speed.

Normally ships move in different patterns -- up and down, east-west or north-south pattern or on reciprocal courses or in a pattern. They keep moving because being stationary for a long time is hydrographically uncomfortable for any ship.

There are only one or two conditions when a ship is stationary. When it wants to conserve fuel or has no operational tasks and, generally, when the sea is very calm. Otherwise, a stationary ships rocks and rolls a fair bit.

If indeed the Iranian warship was stationary at that point of time when the photograph was taken, then that would have been for a brief instant -- maybe while the crew was carrying out some repairs or something specific that needed it to be stopped.

Otherwise, ships do not stay stationary for long periods.

What advantages does a nuclear attack submarine have over other ships?

Stealth and speed.

In most cases, they can approach a target without being detected.

This advantage is even greater in the Indian Ocean with its warm water hydrographic conditions, unlike the cold Pacific or Atlantic.

Conventional submarines have to come to surface or snorkel more often to get air to recharge their batteries and have certain speed limits.

A nuclear attack submarine, however, can go underwater from the time she's left the harbour, which could be, say, Diego Garcia or any other port and generally remain undetected, unknown to anyone except her national authorities.

She can thus, reach her intended destination or target at a certain place and time covertly.

In theory, a nuclear submarine can stay underwater for as long as its nuclear reactor is operating. It is other factors like crew endurance and their psychological well-being which may require the submarine to return to port.

It may also surface in shallow waters where operating at depth is not possible.

Technically, however, there are no major limits on its underwater endurance or speed. This removes many of the opportunities an adversary might otherwise have to detect or intercept it.

How can a nuclear attack submarine be detected?

It needs great effort to detect a nuclear attack submarine. It needs intelligence and planning to gauge where the enemy may put its assets and then deploy sophisticated anti-submarine warfare assets.

Anti-submarine resources include seabed sensors or chain of monitoring devices, long-range maritime patrol aircraft equipped with sonobuoys and magnetic anomaly detectors and helicopters, and ships fitted with sonar systems and sonobuoys. Add to this satellite-based sensors, electronic intelligence and human intelligence. Axiomatically, that means tremendous resources.

Even then, tracking or intercepting every nuclear submarine at sea is very difficult, even for formidable naval powers. Therefore, they concentrate on certain nations based on their threat perceptions.

Nations also rely on geography for tracking and intercepting hostile vessels. For example, in India's case, it could by keeping a watchful eye on the Malacca Straits or the Sunda Strait or the Lombok Strait or similar such chokepoints or narrow waterways elsewhere in our areas of interest.

It would be quite a task for even powerful countries like the US to detect, say, every Chinese, Russian or Indian submarine in the Indian Ocean. Oceans are extremely opaque and detecting a nuclear submarine requires tremendous sophisticated resources.

Therefore, it would be challenging for country like Iran to detect and intercept a nuclear submarine attack?

For a country with limited resources -- such as Iran in this context -- it is even more challenging. A surface ship may have only an anti-submarine helicopter and, perhaps, a sonar system for submarine detection.

The probability of detecting and identifying a nuclear submarine under such circumstances is likely to have been low. If the submarine was detected at all, it may have been too late -- much like a classic jungle ambush where the target realises the threat only when escape is no longer possible.

Another uncertainty is the state of readiness of the ship involved. We do not know whether it had been forewarned of a possible submarine threat or instructed to take precautionary measures.

Without such forewarning, it is entirely possible that the ship was unaware of the submarine's presence and was effectively taken by surprise. That is the broader operational context in which an incident like this could occur.

How did you think the hunt and kill must have happened?

Once the submarine detected the surface ship, it launched the MK-48 torpedo which broadly has a range of 20 kilometres, about 12 nautical miles.

Given the prevailing conditions and this context, the Iranian ship was, probably, a sitting duck and all that the US submarine had to do was to get the fire control solution and launch the torpedo.

Whether the submarine sent out one torpedo or more, we do not know.

Clearly in this case, the submarine has come up to the periscope depth because they have released visuals of the Iranian ship.

Subs usually come on to periscope depth only when reasonably certain that they will not be detected or simply because the commander has the courage to take that risk.

Another reason is to confirm the target because no matter how good your sensors are, you may want to visually verify that the ship you are hitting is indeed the intended target.

Hitting the wrong ship has massive consequences.

The sub would have then aligned itself for the best fire control position and shot the torpedoes.

Torpedoes are the most effective way to hit a ship. Missiles fired from a submarine or an aircraft or other ships strike a vessel above or close to the water level.

While even missiles can destroy ships, but in those cases the damage can be contained if there is no large-scale flooding such as what a torpedo hit may cause. Sometimes, missiles also pack lesser warheads than a torpedo. But that's not a blanket rule.

A torpedo, particularly in this case, detonated beneath a ship and creates a huge column of water with great force that sends shockwaves up the ship.

It explodes the ship's hull. Not only does water gush in, it's entirely possible that the entire electricity fails. People are trapped in whichever compartment they are in the bowels of the ship.

There could even be a sympathetic detonation, which means that other ammunition on the ship also explodes, leading to further fires and floods.

The attack took place late night-early morning which is the 'golden hour' to launch an attack on the enemy?

Yes, the reason for it is to catch the enemy unawares. Pre-dawn hours are when human reactions are a little slow; visual detection abilities are lower and troops are most likely asleep. It is considered the most opportune moment to launch an attack to maximise the damage.

Torpedoes travel at more than 100 kilometres per hour, about 50-60 knots. It must have been a matter of a few minutes before it detonated under the Iranian ship. The Iranian ship would have probably got three, four minutes and wouldn't have known till they actually heard the whirr of the torpedo -- and that is assuming they were keeping an anti-submarine watch -- meaning they are specifically looking and listening for underwater threats.

Torpedoes make a particular sound and to hear an incoming torpedo, ships need to have their passive sonars turned on.

Trained seamen can pick up the distinctive sound of torpedoes, but that again depends on the crew's level of training. They need to be skilled to distinguish the sound of a torpedo from other sounds of the sea -- like shifting water columns or water animals or the noise of another submarine.

• THE MIDDLE EAST CONFLICT

It is reported that the Iranian warship was unarmed. Is it a standard practice that participating ships in an International Fleet Review sail without weapons?

The Indian Navy or fleet review events do not prescribe the arming policy of visiting ships. This is decided by respective national authorities. Please remember that naval vessels are sovereign territories of nations wherever they go. They are the only entities allowed to fly the flag of their countries across all seas.

Decisions about how heavily a ship is armed is the sole prerogative of individual countries. The Indian Navy or the fleet review doesn't give any instructions about arming of visiting ships.

The standard practice is that during a fleet review, ships may be asked not to load ammunition in their guns or align the barrel of their guns in a neutral direction as a safety measure. So that when a VIP or reviewing vessel passes, the guns are not aiming towards them.

These instructions are local and specific to the particular time and space.

When ships are in another country's waters, the host navy can prescribe certain operational instructions -- not orders -- during exercises or ceremonial events. These are simply precautions to avoid accidents or friendly-fire incidents

But once a ship leaves territorial waters, beyond the 12 nautical mile limit, she enters international waters and is completely free to decide its arming, readiness and operational course of action.

But, most warships sail reasonably well armed. There is no such thing as being unarmed or going unprepared or unequipped. That simply does not behove any warship of a professional navy.

• Part 2 of the Interview: 'War Is Brutal. At Sea, Even More Brutal'