Subsurface forces
Submarines are one of the most powerful warships in modern warfare. The only capital warship sunk after 1945 was sunk by submarine. Submarines of minor navies, such as Norway and Israel, have on occasion shown up the defences of American carrier task forces. Anglo-Norwegian subsurface forces would have wreaked havoc on Soviet surface elements attempting to force landings in Iceland and Norway in a Hot War.
Submarines can reliably be used to attack capital warships, surface installations, and other submarines. They can lay mines in the advance of a hostile naval formation, or outside ports. The presence of a submarine in an area makes commanders cautious and nervous. In terms of area-denial there exists no better weapon then a submarine.
Yet, submarines do not possess serious defensive weaponry (some Russian subs do store MANPAD) and are not armoured to withstand serious attack. When caught, they will be skinned alive by even the smallest of surface ships. So why are they so powerful?
Submarines can reliably be used to attack capital warships, surface installations, and other submarines. They can lay mines in the advance of a hostile naval formation, or outside ports. The presence of a submarine in an area makes commanders cautious and nervous. In terms of area-denial there exists no better weapon then a submarine.
Yet, submarines do not possess serious defensive weaponry (some Russian subs do store MANPAD) and are not armoured to withstand serious attack. When caught, they will be skinned alive by even the smallest of surface ships. So why are they so powerful?
Detection of subsurface forces
Submarines are quiet. Their only defence is their ability not to be seen. The method of detection for submarines is Sonar, which is an acoustics detection method. The ocean creates around 90 decibels of background noise; the most modern submarines generate, on a slow cruise, less noise than this. Of course, emitting sonar causes its own problems, but we can see that the detection of submarines is not a laughing matter. It can be done in a number of ways, all of which should be used by an intelligent commander.
Magnetic Anomaly Detection
A MAD system is designed to detect variations in the lines of magnetic force around the earth. A great mass of ferromagnetic material like a submarine significantly alters the magnetism of the ocean. MAD detectors are mounted on aircraft and represent one of the most modern forms of anti-submarine detection. On the other hand, submarines can be disguised by titanium construction, since titanium has reduced ferromagnetism. This is a partial, not complete defence against MAD. The intelligent reader will have surmised that the larger a submarine is, i.e. the greater weight of ferromagnetic material that is in the water, the more open it is to magnetic anomaly detection.
Dipping Sonar
Anti-submarine warfare (ASW) helicopters can deploy sonars from a winch that dip into the ocean, known as "dipping sonar." The advantages of this are obvious: the submarine can not attack the source of the sonar, and the submarine is detected from a safer distance than by ship-based sonar. The secondary effect is that a ship can hide from a passive sonar on a submarine, if that submarine is emitting.
Sonobuoys
Sonobuoys represent a more strategic and less tactical approach to subsurface detection. Sonobuoys can be deployed by fixed wing aircraft or helicopters and are essentially a flotation device with a datalink, which deploys a microphone at some depth in the water. This microphone listens for noise in the water that might be as submarine, for instance, the noise of a submarines propulsion system. Sonobuoys can be deployed in such a manner that provides cross-fixing over a large area. Land-based fixed wing aircraft can store great quantities of sonobuoys and can stay on station for long periods of time.
Ship sonar
This is the least useful of all. You will have noticed that the first three methods of detection are done by fixed wing or helicopter units. Emission of active sonar gives away immediately the position of a ship to a submarine which might then attack with a missile or torpedo. Ship sonar should only really be used when there is a very high possibility that a submarine already knows the location of the emitting vessel.
N.B. Radar can in theory be used to detect a surfaced submarine, but remember that the reach of a radar's power is longer than its useful range: the submarine's own ESM system will detect the radar before it is detected, if it is far away enough, and submerge. This is only a useful method if the aircraft begins emitting when the submarine is in range, i.e. it is only useful by chance and not intent.
Magnetic Anomaly Detection
A MAD system is designed to detect variations in the lines of magnetic force around the earth. A great mass of ferromagnetic material like a submarine significantly alters the magnetism of the ocean. MAD detectors are mounted on aircraft and represent one of the most modern forms of anti-submarine detection. On the other hand, submarines can be disguised by titanium construction, since titanium has reduced ferromagnetism. This is a partial, not complete defence against MAD. The intelligent reader will have surmised that the larger a submarine is, i.e. the greater weight of ferromagnetic material that is in the water, the more open it is to magnetic anomaly detection.
Dipping Sonar
Anti-submarine warfare (ASW) helicopters can deploy sonars from a winch that dip into the ocean, known as "dipping sonar." The advantages of this are obvious: the submarine can not attack the source of the sonar, and the submarine is detected from a safer distance than by ship-based sonar. The secondary effect is that a ship can hide from a passive sonar on a submarine, if that submarine is emitting.
Sonobuoys
Sonobuoys represent a more strategic and less tactical approach to subsurface detection. Sonobuoys can be deployed by fixed wing aircraft or helicopters and are essentially a flotation device with a datalink, which deploys a microphone at some depth in the water. This microphone listens for noise in the water that might be as submarine, for instance, the noise of a submarines propulsion system. Sonobuoys can be deployed in such a manner that provides cross-fixing over a large area. Land-based fixed wing aircraft can store great quantities of sonobuoys and can stay on station for long periods of time.
Ship sonar
This is the least useful of all. You will have noticed that the first three methods of detection are done by fixed wing or helicopter units. Emission of active sonar gives away immediately the position of a ship to a submarine which might then attack with a missile or torpedo. Ship sonar should only really be used when there is a very high possibility that a submarine already knows the location of the emitting vessel.
N.B. Radar can in theory be used to detect a surfaced submarine, but remember that the reach of a radar's power is longer than its useful range: the submarine's own ESM system will detect the radar before it is detected, if it is far away enough, and submerge. This is only a useful method if the aircraft begins emitting when the submarine is in range, i.e. it is only useful by chance and not intent.
Where to hide and where to run?
Submarines are not helpless by any measure. Their commander has a great deal of tactical options open to him to avoid detection.
He must understand that he can never really know when there are enemy aircraft operating ahead. The deployment of dipping sonar or a sonobuoy will be detected by the submarine, but the use of MAD equipment can never be known. It's important then for a submarine commander not to emit. He should use his sonar actively only when completely necessary, for passive listening techniques have their own uses.
Subsurface noise
One can appreciate that a ship is a loud thing underwater. Next time you are at a swimming pool, hold your head underwater when someone jumps in. (Don't look like a retard when you are doing this, though, and under no circumstances tell anyone you are "learning about the principles of acoustic detection.") You can hear the noise. A submarine's listening equipment listens for subsurface noise and translates that noise into ideas about what the noise could be. For instance, the noise of a six-blade propeller is distinctively different to a sonar system than is a five-blade propeller. Larger engines vibrate more than smaller engines. Sonar operators on HMS Conqueror reported hearing noises "like a breaking chandelier" after they sank ARA General Belgrano.
A highly sophisticated passive listening system can hear the movement of surface vessels by listening to their propellers. This makes submarines critically useful in reconnaissance. It also means that they do not need to emit to "stalk" an enemy force; they can carry on behind it by just listening to the noises it makes when it moves.
In a combat situation, a submarine has a great advantage. It has a peak time between firing a torpedo -- which is very loud, and will give away the submarines position -- and the explosion of that torpedo, which will generate a tremendous amount of noise and "mask" the submarine, whereby it will be very visible. If the submarine is lucky and hits its target, the explosion and the noise of a sinking ship will mask it to a great extent. If it misses, everyone will know its rough position, as long as they are paying attention.
Imagine yourself in a dark warehouse. You are trying to escape from a number of people following you. The only senses that anyone has are touch and hearing. The most intelligent thing to do in this situation is to create a lot of noise very far away from you by throwing things, moving things so that they will eventually fall, so on and so forth. Every background noise made will make your footsteps less heard and your escape -- or approach -- more likely. If you haven't figured it out yet, you are the submarine. The other people in the warehouse are the surface ships, the helicopters, and the fixed wing ASW aviation that is coming for you.
Good luck.
He must understand that he can never really know when there are enemy aircraft operating ahead. The deployment of dipping sonar or a sonobuoy will be detected by the submarine, but the use of MAD equipment can never be known. It's important then for a submarine commander not to emit. He should use his sonar actively only when completely necessary, for passive listening techniques have their own uses.
Subsurface noise
One can appreciate that a ship is a loud thing underwater. Next time you are at a swimming pool, hold your head underwater when someone jumps in. (Don't look like a retard when you are doing this, though, and under no circumstances tell anyone you are "learning about the principles of acoustic detection.") You can hear the noise. A submarine's listening equipment listens for subsurface noise and translates that noise into ideas about what the noise could be. For instance, the noise of a six-blade propeller is distinctively different to a sonar system than is a five-blade propeller. Larger engines vibrate more than smaller engines. Sonar operators on HMS Conqueror reported hearing noises "like a breaking chandelier" after they sank ARA General Belgrano.
A highly sophisticated passive listening system can hear the movement of surface vessels by listening to their propellers. This makes submarines critically useful in reconnaissance. It also means that they do not need to emit to "stalk" an enemy force; they can carry on behind it by just listening to the noises it makes when it moves.
In a combat situation, a submarine has a great advantage. It has a peak time between firing a torpedo -- which is very loud, and will give away the submarines position -- and the explosion of that torpedo, which will generate a tremendous amount of noise and "mask" the submarine, whereby it will be very visible. If the submarine is lucky and hits its target, the explosion and the noise of a sinking ship will mask it to a great extent. If it misses, everyone will know its rough position, as long as they are paying attention.
Imagine yourself in a dark warehouse. You are trying to escape from a number of people following you. The only senses that anyone has are touch and hearing. The most intelligent thing to do in this situation is to create a lot of noise very far away from you by throwing things, moving things so that they will eventually fall, so on and so forth. Every background noise made will make your footsteps less heard and your escape -- or approach -- more likely. If you haven't figured it out yet, you are the submarine. The other people in the warehouse are the surface ships, the helicopters, and the fixed wing ASW aviation that is coming for you.
Good luck.
Asymmetrical uses of subsurface forces
There are more than one uses of a submarine, other than directly attacking enemy warships. Indeed, the submarine is a versatile weapon. All rely on the submarine's ability to move undetected more easily than surface warships.
Insertion of SOF
Special forces troops can be deployed via submarine, making their insertion vastly stealthier. RIBs can be deployed close to shore and then the submarine can submerge again. This method of SOF deployment can only be countered by the most thorough and paranoid of subsurface detection routines
The laying of mines
Mines can be laid by submarines in busy shipping lanes, in the path of an advancing enemy force, or in the mouth of a port or bay to block extraction of enemy units, or in the advance-defence of an expected enemy amphibious landing.
Reconnaissance
The "stalker" of the seas, submarines can follow surface fleets at close or far distances, occasionally using satellite masts to communicate the location of the enemy and the composition of their force to a superior commander. The principle that the longer something is observed, the more is known about it also applies to submarines, who can stalk an enemy for hours or days.
Shore bombardment
In the wake of the 9/11 attacks, the response by the USA in the form of a huge bombing campaign based out of Diego Garcia and from aircraft carriers is well known and documented. Less known is the Royal Navy response in the form of Tomahawk cruise missiles launched from a Trafalgar class submarine. Submarines, especially SSGNs, can be equipped with surgical strike weapons to attack shore targets. They possess a strong advantage in that they're not directly visible.
Deployment of nuclear weapons
USA, Russia, France and Britain all possess subsurface nuclear forces. It goes without saying that submarine-launched ballistic missiles are an essential part of a nuclear deterrent. In fact, Soviet naval strategy focused heavily around 'bastion defence' of SSBNs, with most surface ships being used to protect the areas in which Soviet nuclear subs operated.
Insertion of SOF
Special forces troops can be deployed via submarine, making their insertion vastly stealthier. RIBs can be deployed close to shore and then the submarine can submerge again. This method of SOF deployment can only be countered by the most thorough and paranoid of subsurface detection routines
The laying of mines
Mines can be laid by submarines in busy shipping lanes, in the path of an advancing enemy force, or in the mouth of a port or bay to block extraction of enemy units, or in the advance-defence of an expected enemy amphibious landing.
Reconnaissance
The "stalker" of the seas, submarines can follow surface fleets at close or far distances, occasionally using satellite masts to communicate the location of the enemy and the composition of their force to a superior commander. The principle that the longer something is observed, the more is known about it also applies to submarines, who can stalk an enemy for hours or days.
Shore bombardment
In the wake of the 9/11 attacks, the response by the USA in the form of a huge bombing campaign based out of Diego Garcia and from aircraft carriers is well known and documented. Less known is the Royal Navy response in the form of Tomahawk cruise missiles launched from a Trafalgar class submarine. Submarines, especially SSGNs, can be equipped with surgical strike weapons to attack shore targets. They possess a strong advantage in that they're not directly visible.
Deployment of nuclear weapons
USA, Russia, France and Britain all possess subsurface nuclear forces. It goes without saying that submarine-launched ballistic missiles are an essential part of a nuclear deterrent. In fact, Soviet naval strategy focused heavily around 'bastion defence' of SSBNs, with most surface ships being used to protect the areas in which Soviet nuclear subs operated.