Thursday, 22 October 2009

Littoral Warfare

The phrase "littoral environment" is often taken to mean "low threat environment" when in fact it is the highest threat environment a warship could find itself in.

This is what littoral combat looks like:

The Americans seem to be particularly confused in this regard.

The United States Marine Corps bases it's entire amphibious doctrine around Over The Horizon (O.T.H.) assault in order to keep it's troop packed ships beyond the reach of littoral threats.

The United States Navy on the otherhand builds highly capable (but extremely expensive) Zumwalt class "land attack destroyers" to survive in the littoral environment.

Simultaneously and quite perversely the United States Navy is also building dedicated Littoral Combat Ships (L.C.S.).

The latter have weapons and sensors suited only to low threat environments and hulls and machinery suited to nothing more naval than waterskiing,yet they cost more than a full capability frigate.

In "blue water",beyond the weapon/sensor horizon of the coast (typically about 25 miles offshore),ships face threats from submarines,warships,aircraft and mines.

In "green water",within the weapon/sensor horizon of the coast,ships face these same threats but with the addition of land based threats from hostile ground forces.

This "green water" environment poses a number of challenges.

Firstly,the submarine threat is increased both because it is more difficult to detect submarines in the sonar conditions close to shore and because the warships will be exposed to "submarine ambush".

The limited submerged speed and endurance of diesel electric submarines precludes chasing surface ships which can simply run away from them in open ocean.

However,if the warship must enter the enemy littoral,the submarine may lie in wait or it.

Secondly,threats from surface ships increase because enemy vessels can use the coast for concealment and protection and receive support from shore based weapons and sensors.

The doctrine of the Baltic navies and others is based around such tactics.

Thirdly,the air threat is increased,the proximity of land limits the range of the ships sensors and thus reduces engagement times.

Also,air power is inversely proportional to the range at which it is applied.

As the warship approaches the hostile coast it also approaches enemy air fields and hence the combat power of the enemy air force increases in the littoral.

Fourthly,the mine threat increases in the littoral as many types of mine are more effective in shallow water,particularly pressure mines,and also because the more confined waters make approach routes more predictable and hence mineable.

All of the above threats demand much the same kind of warship as might be needed in "blue water" but the threat of attack by land based "army" type weapon systems is unique to the littoral.

These threats can be subdivided into "green water" threats and "brown water" threats,which are a subset of "green water" threats.

On rivers and close to the coast ships will face the most common land based weapon systems ranging from small arms fire up to tank and mortar fire.

Usually only small boats and landing craft would be exposed to these "brown water" threats which rarely extend beyond 5 miles from the coast.

Critical spaces on such vessels may easily be protected against likely threats as they make up a small percentage of the vessels overall volume and space and weight constraints are less demanding on a boat than on a land vehicle.

During the Falklands War a more substantial warship,the corvette Guerrico was exposed to "brown water" threats and did not come off well,see here:

Ironically,she is just the sort of vessel many regard as a "littoral combatant".

Beyond "brown water" and out to the edge of "green water" the land threat consists of heavy and field artillery.

These are major threats to even large ships and although surface combatants may conduct counter battery fires,it is not easy for them to detect and engage concealed artillery observers or to hit mobile artillery systems concealed by the terrain.

Large landing ships cannot enter hostile "green water" to quickly land heavy army units by landing craft and lighterage unless these threats have been neutralised.

Surface combatants are similarly at high risk in this environment.

Consequently the most useful ships in this littoral environment are the air attack ship and the air assault ship,both of which can dilute the threat in the littoral without exposing themselves to "green water" threats.

Combat aircraft and assault troops with surface to surface and surface to air artillery reduce the threat level in the littoral,allowing surface combatants to come in to "green water" extending the range of naval gunfire further inland until the environment is secure enough for landing ships to put army heavy units ashore.

The design requirements for a littoral surface combatant then are much the same as those for a blue water warship only yet more demanding.

The full range of antiship,anti submarine and antiaircraft capability is needed with the addition of a land attack capability.

All of these capabilities must be first rate for a ship to survive in the littoral environment.

The ship must also be highly survivable,it is noteworthy that none of the elderly Royal Navy warships in the Falklands was sunk.

All of those vessels lost were newer Type 21 frigates and Type 42 destroyers,ships built to lower construction standards due to financial constraints in the 1970s.

A larger hull is particularly helpful with regard to survivability,it also permits a taller radar mast which allows targets to be detected at longer ranges.

There are very few areas of sea where a warship of less than 10,000 tonnes cannot get within weapon/sensor range of the coast.

There are areas where such a ship cannot physically get near to the coast but there is little need for it to do so if it is equipped with adequate large boats.

Small rigid hulled inflatable boats cannot independently stand up to threats such as this:

Large boats can operate in higher threat environments and have greater range,endurance,seakeeping and payload capabilities.

Such boats can operate with a high degree of independence while performing tasks such as boarding,landing,piqueting,mine hunting,mine laying,surveying,patrolling and even sub-chasing.

Big hulled frigates can carry,support and protect large boats.

The constitution of a littoral navy then is similar to a blue water navy but with a need for more capable and survivable surface combatants,aircraft carriers which perform land attack missions in addition to air defence and antisubmarine roles and a requirement for amphibious air assault ships.

A littoral navy can also perform the tasks of a "blue water" navy.

Such a fleet is not very different to what the Royal Navy is at present trying to become.


cbd said...

Generally agreed...but I think the example of the Guerrico is a bit heavy handed and, moreover, not particularly helpful to your argument. The tactical errors of its commanders (moving to within 1/2km of the target, too close for a proper solution) and the rapid success consequent to the proper employment of this vessel(NSFS, from beyond small arms range) serves more to contradict your point than defend it.

The Argentyne landing was, it seems, poorly coordinated. Rather than landing aeromobile forces in protected, strategically useful locations, they sought to land on open ground and came within small arms range.

The British tactics allowed for the successful exploit of these errors. Given some more men and resources, the Royal Marines might have held their ground.

The main lesson of this post seems to fall towards the need for alert commanders and WWII-style damage control infrastructure on each ship (moderate steel armoring inherent to the hull, small watertight compartments.

As far as landing craft, I doubt that they would have to contend with an IRGC boat with a fixed-orientation AA gun with limited depression. The whole point of a littoral ship is its ability to remove such threats, rather than become prey to them.

The Zumwalt as a littoral ship is ridiculous, as is the LCS, but is a Burke better? The Type 23?

It's a real shame the INS Hanit was found napping on the job--a combat test of modern air defense and CIWS would have been nice.

tangosix said...

Hello cbd,

that a vessel like Guerrico should not be exposed to those infantry weapons was the point I was making.

The picture of the Iranian boat was intended both as a reference to the fate of H.M.S.Cornwall's boarding party and a generic example of the small boat threat.