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Commander Frank Thiede joined the German Navy in 1984 as a Seaman. First serving as NCO (only on submarines), he became an Officer in 1993. He was the Commanding Officer (CO) on U 18, a 206A class submarine and/or more than four years the very first CO on U31, first of its class U212A submarine. He sailed her during all sea accepta11ce trails. CDR Thiede also served as Staff Officer Operations in the German Submarine Flotilla, as Deputy Commander in the Submarine Training Centre, as Senior Instructor Underwater Wa1fare Operations in the German Navy Tactics Centre and as Subject Matter Expert in NATOs Centre of Excellence for Operations in Confined and Shallow Waters (COE CSW). Today CDR Thiede is working at the Supreme Headquarters Allied Powers Europe (SHAPE) in Belgium as a Strategic Planner.

The role of conventional submarines

In World War II conventional submarines provided an impressive demonstration of their unique capability to disrupt maritime sea lines of communication and the ability to operate independently. With the rise of the nuclear powered submarine after the war, the operational focus of conventional submarines (SSK) concentrated closer to coastal areas.

As a Submariner I have often been asked the same question: “how are conventional submarines used today in confined and shallow waters and what will their role be in the future? And, what capabilities will these valuable assets require? The prevailing operating conditions, shallow water, increased shipping density, complex sound propagation makes detection but also counter detection of submarines often very difficult. In these waters the geography, the proximity to the shore and shallow waters limit the freedom of maneuver for all kinds of sea traffic.

In the past, the operational focus of maritime warfare was on the blue water. Today we are concentrating on the fact that the main maritime traffic routes intersect in waters close to the shore. Everything starts and ends in confined and shallow waters. Consequently it is this area, a subset of the littoral theatre, which, from a naval perspective, has to be successfully controlled in order to safeguard global trade, prosperity and peace.

Nuclear powered attack submarines (SSN) are operated as hunting submarines, eavesdrop-ping off hostile coasts or acting as most powerful and valuable assets in strike operations (SSN and SSGN). Due to their comparatively large size, their suitable area of operation is the open ocean-in other words-Commander Fra11k Thiede blue water. It has often been done, but I doubt it to be feasible-and certainly unsafe-to operate even a smaller nuclear boat in the confined and shallow waters, when it is probably continuously nailed to periscope depth. The maximum size of submarines to operate unimpeded in such a challenging area is limited and depends on the required minimum water depth and maneuverability in shallow water. Due to its size the conventional submarine has an unbeatable advantage in this domain. Unfortunately this comes with its own limitations. SSKs, in the main, operate independently and alone. Integration into a maritime task group or force is difficult; the relatively slow speed of a SSK does not make it the first choice for being an integral part of a force.

Technically, the capabilities of conventional submarines have significantly improved since the 1990s. The introduction of air independent propulsion (AIP) is one important example. Conventional submarines operating air independently (SSK-AIP) have a decisive tactical advantage against SSKs or SSNs, the capability to operate stealthier. Stealthiness is closely followed by a commitment to remaining undetected in order to execute highly sensitive missions. Any submarine must prevent counter detection. Even if an SSK-AIP is not able to match the speed of an SSN, it provides a serious threat due to its capability to remain almost undetectable over a certain period of time.

Before the dissolution of the Warsaw Pact, the focus was on Anti-Surface Warfare, simply to sink surface vessels, and on Anti-Submarine Warfare. The wartime mission of submarines was sea denial in order to render a sea area inaccessible for an opponent. Since the end of the Cold War, the requirements for the use of conventional submarines have changed significantly. Their core mission has evolved from the protection of own and disruption of enemy sea lines of communication, to the fight against surface vessels and Anti-Submarine Warfare. Submarines are now increasingly operating in regional high intensity conflicts or fast developing conflicts and crises. Thus potential areas of operation shifted from the open sea into the coastal waters. In today’s maritime influenced or supported operations, the SSK’s-much like the SSN’s-are primarily used for (a) Intelligence, Surveillance and Reconnaissance, the collection and pre-analysis of information by acoustic, electromagnetic, optical and optronic sensors, (b) for Indication and Warning, (c) the selective use of a submarine for obtaining essential, time critical information for an operation and (d) for support of Special Forces, including the covert deployment of personnel. But SS Ks can perform these tasks a Jot closer to the shore than the SSN. The variety of scenarios today includes not only missions covering the classic warfare areas but also, for example Maritime Interdiction Operations, Counter-Piracy or Counter-Drug Operations. A surface Critical Contact of Interest for example will notably mask its suspicious behavior when sighting or detecting an approaching Navy or Coast Guard ship, helicopter or aircraft. It will probably not, when a submarine approaches at periscope depth, collecting all kinds of data and evidence, reporting to a higher authority, ordering and coordinating follow on actions.

Much better than their non-AIP predecessors, future SSK-AIP’s will be able to operate efficiently in blue waters; however, the required capabilities of tomorrow’s submarine must be based on the requirement to conduct operations in confined and shallow waters.

The role of a conventional submarine has to be understood less as a lone wolf and more as an integral part of a Task Force or Task Group. To be as effective as possible in these missions, certain capabilities for submarines are required, which will be determined now. The submarine is the ideal advanced and covert sensor. Submarines are able to operate in hostile waters and prepare a battle space prior to major operations. To contribute as much as possible to a maritime operation, the submarine has to act in direct support; in other words, all movements are ordered and controlled by a Task Force Commander, specified tasks are given directly. If the submarine is operating in associated support, all tasks have to be requested via a Submarine Operating Authority. Direct support requires two major capabilities for submarines: (I) two-way communications at almost any time and (2) speed.

Experience shows that the success and benefit of a submarine deployment in a maritime operation depends on the ability to communicate large amounts of data in near real-time in order to operate as a part of a Team, participating in network-centric operations. The availability of current and comprehensive information is a prerequisite for all successful military operations. The rapid dissemination of all information enables the Area or Force Commander and the political decision-makers to make sound decisions. On the other hand, for a Submarine Commander, easy access to intelligence information is often essential to operate the submarine as effectively and safely as possible in order to accomplish its mission. Furthermore, the control of a submarine to prevent mutual interference and to coordinate the water space management, to enable action against an enemy submarine in a friendly submarine operating area, requires the capability of secure, stable two-way broadband communications and the ability to participate in both above and underwater networks. The decision to expose the submarine’s position by using hoistable masts like periscopes or antennas or by acoustic and electromagnetic transmission will always be made by the submarine commander. His decision will be based on the tactical situation and the prioritization of his given orders.

SSK technology and challenges

The acoustic signature of state of the art SSKs has been reduced significantly. During the submerged transit modem electric motors are driven by energy from advanced, powerful batteries and/or air-independent power systems, such as fuel cells. Additionally, these boats are hybrid, i.e. still require diesel engines/generators to charge the batteries and of course a snorkel. But whenever speed is required, AIP-propulsion is not yet the perfect solution due to the relatively low speed attainable with fuel cells or Stirling engines. The conventional lead-acid or very soon the lithium-ion battery will-for the foreseeable future-be indispensable for high speed.

And it is speed, that is essential for everything that has been discussed in this paper. A modern conventional submarine in the future must be able to shift its focus or the focus of its operations in a relatively short time by a few hundred nautical miles and it must be able, at least partially, to keep up with the speed of advance of a Task Force in order to act in direct support.

For supporting Special Operation Forces Missions, certain available sensors and effectors are of particular importance. Prior to deploying the forces, a valid, detailed and accurate operational picture must be provided. In addition to the information of acoustic, electromagnetic, optical and optronic sensors, the use of small UAVs in coastal areas extends the capabilities and the horizon or the line of sight of a submarine. The submarine must be able to deploy a certain number of personnel safely and covertly within minutes. Additional payloads, sometimes in larger size like delivery vehicles or canoes, have to be transported. The ability to provide limited fire support for Special Forces, for example with small missiles capable of attacking land targets, would complete the mission profile.

The basic design of submarines and the classic use of this system have changed only slightly in history. SSKs are mainly designed to fire heavy weight torpedoes, either wire-guided or as a fire-and-forget weapon. These weapons are configured to attack submerged and surface targets. The necessary data collection and target motion analysis is done by passive and active sensors in combination with a modem highly sophisticated fire control system.

From open sources it is evident that since the end of the Second World War, only three surface vessels have been sunk by submarines in war or close to war scenarios. Conventional and nuclear-powered submarines have successfully executed sea denial during the Cold War and several local conflicts. These assets tied down extensive maritime forces, which had to be used for Anti-submarine Warfare and for protection of own forces and thus were not available for other operations.

There is no question about it, that the capability for Anti Surface Warfare is still mandatory for future conventional submarines. This applies equally to the capability of detecting and fighting other submarines and to sustaining operations in a conflict. However, we have to consider whether in future operations an SSK equipped with usually six or more torpedo tubes and a corresponding payload of heavyweight torpedoes is required, or an additional capability can be achieved by equipping the submarine with other components at the expense of a large torpedo load. The same applies to the question, how much effort has to be spent in the future on close to zero signatures. The challenge is to keep required capabilities but reduce the number of torpedoes whenever feasible.


Since the area of operations in confined and shallow waters limits the maximum size of the submarines, efficient use of space is paramount! What modern navies need are highly-sophisticated and flexible conventional submarines with the respective sensors and effectors. The capability to participate actively in network-centric operations, the capability of gathering intelligence, and to onduct surveillance and reconnaissance is mandatory. A submarine can provide, depending on the tactical situation, very valuable information as a covert advanced sensor and integral part of an Information Network. Additionally, the submarine is always capable of switching from Intelligence, Surveillance, Reconnaissance or Indication and Warning to Anti-Surface or Anti-Submarine Warfare, depending on the current situation, requirements and orders. The heavy weight torpedo as the classic main armament is still required for self-defense and for achieving or implementing sustainable sea denial. However, it is the number of torpedo tubes and the load of additional torpedoes which could be limited to use the space on board more efficiently. Potential solutions, like pressure-resistant modules, feasible for different payload like torpedoes, missiles, divers or other payloads tailored to specified missions are already available on the market.

It is clear that conventional submarines will have a place in the fleets of the future. This shows the disposition of modem units worldwide. Even if the purpose of these assets is often described in the classic way, it is reality that these submarines have changed from an offensive, lone weapon carrier to a precious and valuable platform, supporting or being an integral part of a maritime Task Force, but still combined with the capability for immediate offensive action.

Future scenarios need to be analyzed carefully in order to define the required skills and capabilities. Further technical solutions need to be developed and implemented. Navies as users and industry as manufacturers of conventional submarines must be encouraged to work together in close cooperation to share their experience, concerns and their ideas.

At the beginning of this article I raised the questions, how modem conventional submarines will be used in current and foreseeable future operations and what are the required capabilities for co11ventio11al submarines derived from this. I see the role of future SSKs or SSK-AIP as flexible and versatile assets that are adaptable to the evolving maritime security environment. Their stealthy character makes them ideally suited for a variety of missions like Maritime Security and/or Interdiction Operations, Intelligence Surveillance and Reconnaissance, Indication and Warning, Counter Piracy or Counter Drug Operations and to support Special Forces-and Land Operations. The capability to execute sea denial, Anti Surface and Anti-Submarine Warfare requiring an adequate number of torpedoes and or missiles, will be mandatory. It is still valid to assume that 10 Anti-Submarine Warfare assets are required to counter one submarine. From my perspective a future conventional submarine requires the capability to act as a flexible asset, tailored to the given specified mission. At first glance, modules for mission dependable payloads could be a solution. The ability to participate in above-and underwater networks, to communicate in real time and to move at high speed with longer endurance is a must. Submarines are gaining increasing importance in maritime and joint operations in the littorals and, if required, in the blue waters as well. There is no doubt that for the foreseeable future the focus will be on conventional submarine operations in green and brown water.

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