One scenario that was the focus of American naval planning during the Cold War was a conflict between two modern and well equipped fleets on the high seas, the thankfully never occurring clash of the USA and Russia. The main consideration is for Carrier Battle Groups (CVBGs).
It is tempting to regard modern naval combat as the purest expression of tactics -- there is no cover, there are no civilians and the area of combat is level and flat. It is a pity that this isn't true -- the presence of land, changing water depths, weather, detection, air power, the dreadful speed at which actual combat occurs and a number of other factors render naval tactics truly formidable.
The basic idea of all tactics (land, sea and air) is Fire and movement. The delivery of firepower to support a mission and movement is the achievement of scouting and firing positions over any period of time. Movement is especially obvious in modern combat where a fleet can travel hundreds of kilometres in a day.
In naval warfare the key is to detect the enemy while avoiding being detected yourself. And to deny to the enemy the attempt to detect your forces.
There is also the concept of battle space -- a zone around a naval force within which a commander is confident of detecting, tracking, engaging and destroying threats before they pose a danger. This is why a navy prefers the open sea. The presence of land and the bottom topology of an area compress the battle space by limiting the opportunities to maneuver, make it easier for an enemy to predict the location of the fleet and make the detection of enemy forces more difficult. In shallow waters the detection of submarines and mines is especially problematic.
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2 Fleet Formation 3 Detection 4 ASW Operations 5 AAW Operations 6 AAW Operations 7 ASuW Operations 8 Strike Planning |
Once a commander has considered the geography of an mission he then examines the assets the enemy is believed to have available, the enemy's order of battle (OOB), what units are needed to succeed at the mission objective and the added constraints placed by mission requirements (time etc.). This results initially in a Path of Intended Motion (PIM) for the forces.
As enemy forces are encountered and (hopefully) identified they should be catagorised by potency and immediacy and the OOB altered to reflect this. There are four threat classes: A, B, C and D.
Class A is Potent and Immediate; this is a need to drop everything and respond immediately. This might be a gaggle of sea-skimming missiles racing towards you, or something as powerless as a tug -- which is communicating the fleet's position to a more distant enemy.
Class B is Immediate only; this requires fast action but is not mission threatening. A small boat detected in the outer screen for example.
Class C is Potent only; this is a 'win' for the fleet commander, a significant threat detected at a range where there is time to either mass force to destroy it or to avoid it.
Class D is Neither Immediate or Potent; a target of opportunity which is not a threat and the destruction of which does not aid the assigned mission.
After establishing a path of intended motion the forces must be organised. This depends on the threat axis - an estimate of the likely direction from which an enemy attack will come. A threat axis may change over time. There may be a single threat axis or one for each type of enemy - AAW (Anti-Air Warfare) axis, ASW (Anti-Submarine Warfare) axis and ASuW (Anti-Surface Warfare) axis. The use of more than one axis is uncommon as they are complex to use and confuse the formation.
The positions in the formation are called station assignments. Which unit is placed where depends on the capabilities of the unit. Despite the multi-task abilities of modern units some are more capable at specific tasks than others. AAW and ASW are the important defensive properties, ASuW is usually offensive in nature.
A formation consists of a number of layers of defense. Furthest out are the picket ships, Combat Air Patrol (CAP) craft and early warning aircraft (AEW). These units operate at 200 nautical miles (nm) or more out from the high value units (HVUs). The outer screen is between 12 and 25 nm from the main body and the inner screen is within 10 nm of the HVUs.
The mission of the outer screen is to detect and engage any enemy units that have bypassed the pickets. These units need to be multi-role but there is usually an emphasis on ASW, especially passive detection (it is quieter out there than near the HVUs and so detection is easier). Often there are helicopter ASW assets for 'stand off' engagement. The ships are usually assigned to specific sectors which allows a 'sprint and drift' detection of submarines - the ship 'sprints' to the front edge of its sector, then slowly moves back across the sector. Passive towed sonar arrays operate very efficiently on the return leg. AAW in the outer screen is to protect ASW operations and to attack aircraft before they reach their weapons-launching points, range of defensive weapon is more important than rate of fire here.
The inner screen emphasis is on AAW. The task is to engage any airborne threats that penetrate that far. This means the threat is almost certainly a missile so AAW rate of fire is important. The more defensive firepower in the air the more enemy threats will be destroyed. For ASW the inner screen needs good active sonar. The threat is too serious for passive sonar as immediate targeting is needed. Checking the area around and under HVUs for submarines is called 'delousing'. If possible at least one ASW helicopter is airborne all the time, to target detected contacts as quickly as possible.
In modern naval combat there is the potential of a deadly strike being launched from up to 600 nm away. This is a huge area to scout. The double-edged answer to this is electronic warfare.
Electronic warfare (EW) consists of three elements -- Electronic Support Measures (ESM), Electronic Counter-Measures (ECM) and Electronic Counter-Counter-Measures (ECCM).
ESM is the passive detection of enemy electromagnetic (EM) emissions. The radiated energy of an emitter can be detected far beyond the range at which it returns a usable result to its user. Modern ESM can identify the actual class of the emitter, which helps identify the unit on which it is used. Passive cross-fixing between a number of units can create a reasonably small area of probability. ESM fixes are placed in three classes: Detected, Tracking and Targeted, depending on the accuracy of the fix and whether a unit's course and speed has been derived. Of course for ESM to work the enemy must 'co-operate' by radiating their emitters.
The fact that a passive, over-the-horizon missile is completely deadly creates a central problem for a naval force -- when and even if units should ever radiate, and if not how to detect the enemy?. This is detectability vs. survivability. The need to obtain a targeting solution has to be balanced against the enemy's ability to do the same. Although once a commander feels that the fleet's position is known to the enemy a move to active emissions may be vital to prevent destruction.
The control of emissions is called EMCON (EMissions CONtrol). There are three states, A, B and C. A is no emissions, B is limited emissions (no unique emissions), and C is unrestricted. EMCON is not a blanket condition across the fleet. The surface units can be at A while a sufficiently distant AEW aircraft can be at C.
ECM is both offensive and defensive, covering all methods used to deny targeting information to an enemy. Offensive ECM is usually jamming. This prevents the determination of incoming strikes until the jamming unit is destroyed. Chaff is also used to confuse AAW operations. Defensive ECM also uses chaff as well as Soids, Blip Enhancement and jamming of missile terminal homers.
Submarines are the greatest threat to offensive CVBG operations due to the stealth of modern submarines (anechoic coatings, near-silent magnetohydrodynamic drives etc.), which is the submarine's sole advantage. The move towards shallow-water operations has greatly increased this threat. The cherry-on-top is that even the suspicion of a submarine threat forces a fleet to commit resources to removing it as the consequences of an undetected submarine are too great.
Sonar Operation
In the ocean the main factor affecting sonar operation is temperature. Ocean temperature varies with depth, but at between 30 and 100 metres there is often an marked change -- the thermocline, also simply called the layer. This divides the warmer surface water and the cold, still waters that make up the rest of the ocean. Regarding sonar, a sound originating from one side of the thermocline tends to remain on that side -- it is reflected off the layer change -- unless it is very noisy (active sonar, cavitation, firing weapons, explosions etc.). Pressure, salinity and the turbulence of the water also affect sound propagation.
As in all EW the issue with sonar is passive versus active. Whatever the case the thermocline is the major issue. On passive detection the radiated noise of a unit is only apparent across the layer in a narrow cone, undetectable unless units pass almost directly over or under each other. For a surface unit there is the option then of towing a passive sonar array above or below the thermocline - variable depth sonar (VDS).
A further issue is convergence zones (CZ). Sound waves that are radiated down into the ocean bend back up to the surface in great arcs due to the effect of pressure on sound. Under the right conditions these waves will then reflect off the surface and repeat another arc. Each arc is called a CZ annulus. CZs are found every 33 nm, forming a annular pattern of concentric circles around the sound source. Sounds that can be detected for only a few miles in a direct line can therefore also be detected hundreds of miles away. The signal is naturally attenuated but modern sonar suites are very sensitive. Modern active sonar is limited to 250 dB (decibels). This level of noise can be detected at about ten times the range that is useful to the operator, acting as a giant beacon to any submarine in 100 nm. So a target needs to be nearby and preferably on the same side of the layer to be detected by active sonar; just where a commander would not like a submarine to be!
VDS is designed to solve this problem. The passive array can be put below the layer to detect approaching submarines and when the target is within strike range a brief and unit-selective move to active transmissions can quickly return a targeting solution. The added advantage of VDS is that while it is operatiing below the layer, a unit's hull-mounted systems can be used above the layer.
Unfortunately VDS is a blue-water solution. In shallow water, high levels of biological, wave and tide noise, the influx of fresh water from rivers and the lack of a thermal gradient -- and therefore CZs -- make it a truly dreadful environment to detect a sub-surface threat. Passive detection is almost impossible and surface units are forced to use active sonar to search. The move too close to shore must only be done for mission purposes and there a fleet must act as if they have already been detected and maybe even targeted.
The ASW Triad
For successful ASW, all surface, air and subsurface assets must be used in the most tactically efficient manner. ASW egagements occur in three phases:
Detected - From any source a submarine is possibly (POSSUB) or probably (PROBSUB) in the area.
Localized - A submarine contact has been localized to a sufficiently small area to allow an attack with some chance of success.
Targeted - The submarines bearing, range, course and speed are known with sufficient accuracy to attack with a high probability of success.
Area ASW is the coordination of search ahead of the main force. Detection and localization are the objectives, with destruction if possible. Area ASW is best conducted by units with endurance and potency: maritime patrol aircraft (MPA) at 150 nm out or towed-array equipped surface units 30-50 nm out are most common. If the air unit has magnetic anomaly detection (MAD) as well as sonobuoys then so much the better.
Local ASW is within the outer screen, 12-25 nm from the main fleet. Detection is strictly passive as the distance is still great enough for the HVUs to be safe. Once a contact has been made, helicopter ASW assets (with dipping sonar, MAD or sonobuoys) must be rushed into the area. Three or more passive contacts are rapid enough for aerial delivery of torpedoes. Ship-mounted ASW weapons such as ASROC are reserved for when a contact is too close -- generally less effective -- their role is to distract the submarine from attacking and buy time for a more effective strike.
If a submarine penetrates to the inner screen all and any efforts to distract the submarine from attacking the HVUs must be made. The issue is getting weapons in the water, even if they are not accurately targeted. Torpedo evasion maneuvers are also necessary.
A general maneuver tactic against submarines is a zig-zag. A submarine usually relies on passive detection, not risking active sonar or a periscope observation. So to determine where a unit is heading the submarine needs Target Motion Analysis (TMA). This requires several minutes of passive contact and if the contact starts to zig-zag this process must restart.
The most effective unit to find and destroy submarines is another submarine. Called Hunter-Killers, they utilize the stealth advantage of submarines to track enemy submarines. The difficulty is that they have to be out of communication with the units they are protecting for most of the time to use this stealth. Usually therefore most submarines operate independently within general rules of engagement (ROE) for reconnaissance, ESM and early offensive operations. Modern diesel submarines are almost as efficient as SSNs as Hunter-Killers.
The key threat in modern naval combat is the missile. This can be delivered from surface, subsurface or air units. With missile speeds ranging up to Mach 4 the engagement time may be only seconds.
The key to successful AAW is to destroy the launching platform before it fires, thus removing a number of missile threats in one go. This is not always possible so the AAW resources need to be balanced between the outer and inner air battles.
There are several limitations on Surface-to-Air missiles (SAMs). Modern missiles are commonly semi-active homing. They need the firing unit to actively illuminate the target with a missile fire-control director throughout the flight. If a guiding director shuts down then the missiles still in flight will self-destruct. So the number of intercepts a unit can simultaneously prosecute are limited by the number of directors possessed.
Clearly this is not a good situation and the US Navy has spent vast sums overcoming this limitation. The result was the Aegis combat system - phased-array radar and time-sharing technologies combined with missiles that have an inertial flight mode if the director shuts down.
Airborne Early Warning
The key to successful AAW is AEW. If attacking units can be identified before they reach their launch points then the battle can occur at the outer air-battle screen rather than the inner screen. An AEW unit in a race-track loiter 100 nm ahead of the PIM, with a fighter escort, is perfect.
The Outer Air Battle
In this area the interceptor aircraft of the Combat Air Patrol (CAP) are the principal element, whether originating from a CVBG or land base. CAP units protecting units other than their home base are called LORCAP (LOng Range CAP).
The CAP is most effectively positioned 160-180 nm from the units to be protected on the expected threat axis. At this point the units will wait in a fuel saving loiter to engage incoming groups with AA missiles. As the engagements progress, relief units need to be dispatched to the CAP to ensure that later attacks are met with full weapon loads. If attacking units penetrate the outer defenses they can be intercepted with aircraft in ready-5 status, if used.
The Inner Air Battle
Within the main body AAW shooters should be positioned to provide layered and overlapping coverage. The optimum firing position is directly between the target and the inbound missiles. If the missile passes a unit on a tangent (a crossing shot) the probability of a kill (Pk) is greatly reduced. Aegis equipped units should be kept in close proximity to the HVUs, with less able AAW units no more than 10 nm out along the threat axis with if possible further AAW assets 18-24 nm out.
Other AAW tactics include the use of picket ships in a silent SAM or missile trap. If the main body is forced to use active emissions (they are already detected and localized) the one or two ships can be positioned in emission silence 100-150 nm out. When other units detect an incoming raid the cruisers can go active as the raid moves into their engagement envelope. However if one of these units go active, they are unsupported and are vulnerable to individual attack.
Silent SAM is a technological tactic. Some modern missiles can be fired from one platform with targeting and guidance from another platfrom and need never illuminate the targets themselves.Order of Engagement
Fleet Formation
Detection
ASW Operations
AAW Operations