For effective force protection, it is important for a submarine crew to understand the inner workings of this “system of systems.” The ship’s defense force must clearly understand how it functions as a part of the larger whole. In this article, we will examine not only why a submarine could be a likely target of terrorist aggression, but also what force protection measures crews should expect to implement for their submarines at the pier.

A submerged submarine presents a difficult challenge. Unlike other naval vessels, submarines are built to be essentially invulnerable – but only when submerged. Properly employed, they are nearly impossible to find. There are few sensors that can detect them reliably underwater, and even if located, sophisticated and expensive weapons are needed to carry out a successful attack.  Submerged submarines have little to fear, and classic force protection is unnecessary under those conditions. 

On the other hand, on the surface or in port, a submarine is potentially more vulnerable than most surface platforms. Without significant support, it is ill suited to defend itself, even though its robust construction improves survivability against low-end weapons. Low freeboard, hull shape, and lack of cover and external armament make it difficult to defend the ship and its crew. Additionally, the crew is not large enough to provide an effective perimeter organically. Even so, submarines need to enter port and remain there for a significant portion of their operating life. Regular maintenance and liberty are necessary. Effective forward presence requires engaging our allies, and that requires port visits. Thus, force protection is a fundamental and essential requirement.

Profile of an Attacker
Terrorist arsenals are impressive. Intelligence estimates indicate that an attack by the best-trained and best-equipped terrorists would essentially be indistinguishable from an attack by our own Special Forces, if only because some state-sponsored terrorists receive training from unfriendly Special Forces organizations. Military weapons of significant capability are available on the world market, and their use for terrorist activities is primarily limited only by the capacity to transport them. Sneaking a tracked vehicle or other large armament into the United States for terrorist purposes may prove too difficult, but man-portable military equipment and weapons of opportunity offer no such challenges. The attacks of 11 September also demonstrated the possibility of using non-military items for terrorist purposes. Homemade bombs, vehicles, and industrial chemicals are all available to terrorists to perpetrate an attack. With technical knowledge, access, planning, and some imagination, a terrorist can create enormous disruption without drawing undue attention to his preparations. Since the opportunities are many, and the number of potential weapons is vast, it is very difficult or impossible to predict a terrorist act.

An attacker will spend time assessing the target. He will be patient. He will identify poorly protected avenues of approach. He will measure patterns in the security plan that can be exploited. He will chose a weapon against which the target is poorly defended. He can select a time of attack when defenses are least capable. He may not be concerned with surviving the incident.

With their plan in place, the Cole terrorists sat in Aden, Yemen for several days awaiting the ship’s arrival. Terrorists operate in small “cells,” with each cell responsible for only a single part of the plan. This organization makes them particularly difficult to infiltrate, greatly complicating the intelligence community’s task of predicting these operations. Therefore, it is a mistake to depend on intelligence alone to determine the level to which our ships should be protected.

Defense in Depth
For a terrorist attack on a submarine, we can make some reasonable assumptions about the weapons, manner, and location of potential attacks. They will probably involve man-portable military weapons, a vehicle-delivered explosive, or some threat of opportunity – and they will occur in or near a port. Even limiting the problem in this way, there is enough uncertainty that layers of flexible defense are required for defending a submarine effectively. These layers of overt and covert countermeasures should extend outward from the ship to a distance beyond the expected range of terrorist weapons. Robust, overt security measures serve both to protect and deter if they make clear to would-be terrorists that the target is not worth the investment required to overcome the defenses. If a potential attacker finds a patrolled fence supported by an electronic surveillance system and backed up by a well-armed roving security force, he may decide to look for greener pastures. Covert measures are useful for neutralizing terrorists who attempt to overcome the overt measures. They are effective to the degree that the terrorist is unable to prepare for and defeat them, and for this reason, their specifics should be kept classified and constantly evolving.

The fundamental building blocks of force protection include the following:

• Unambiguous barriers to entry

• Entry control

• Perimeter surveillance

• Area surveillance

• A ready response force

• Onboard point defense

Barriers are key. They prevent access, they can thwart attacks, and they preclude efforts to gather intelligence. Barriers solve the most difficult rules-of-engagement (ROE) problem, determining hostile intent. Security personnel can, on solid authority, engage a party who has crossed a sufficiently robust, unambiguous, and well-posted barrier. Barriers include fences, walls, buoy lines, gates, lifelines, and similar physical boundaries. Properly marked, they are clear lines of demarcation to show that unauthorized parties are not permitted and will be prosecuted – potentially at risk of life and limb – if the boundary is violated.

Waterside barriers provide an unambiguous line of demarcation to assist in determining intent. Recently designed barriers have significant stopping power.

Barriers must be constantly monitored. If a barrier is sufficiently robust, entry at other than official entry-control points constitutes hostile intent and results in immediate action from the security and response forces. Authorized entry occurs only at a limited number of checkpoints where guards have the authority and the means to enforce entry control. Badges or other identification are used by security forces to discriminate between authorized and unauthorized personnel, and vehicles are subject to inspection to ensure that only authorized personnel and material are afforded access. Necessarily, entry points require some relaxation of the integrity of the barrier and therefore require additional security measures to prevent them from being breached by attackers.

Because no barrier is impregnable, and no system is infallible in preventing entry, a well-armed response force is essential to respond to hostile intruders. Only humans armed with a significant variety of firepower and supporting equipment can adapt to the infinite possibilities presented by an attacking force. Enough of a response force should be stationed on site in sufficient readiness to at least delay penetration until additional forces can respond. The criterion remains the same: Attackers must be kept outside weapon-delivery range.

This sonar, optical, and radar equipment (from left) can provide three-dimensional surveillance of restricted areas.

Challenges of the Waterside and Air Defense
Defending a submarine from the waterside adds further challenges. The attacker does not have to contend with formal barriers – but then he doesn’t have them available for cover either. However, he may be able to attack from underwater, approaching close to his target – possibly right up against the hull. But the defender gains a few advantages, too, and with some low-tech equipment, he can defend the waterside as well or better than the land-side. Several effective barrier systems have been developed for use on the water. The most capable can completely arrest the travel of a large motorboat, and the least can provide an unambiguous boundary. Permanent homeports can be outfitted with gated barriers that enclose an area large enough to permit maneuvering within the enclosure, and a larger bounded area provides additional reaction time for defenders should the barrier be breached. All of these measures must be backed up with sufficient firepower from shore or aboard patrol craft to neutralize hostile intruders. Armed patrol boats are both effective surveillance posts and essential response platforms, because they can take advantage of an unobscured view of the entire area and respond on a direct path to the adversary. They can also carry an array of weapons and equipment that allows a response commensurate with the threat. At a minimum, they can delay any credible threat at a safe range until forces arrive that can completely neutralize the enemy. But they must be assigned in sufficient numbers to completely cover the area and respond quickly to any point.

Swimmer detection is difficult. A combination of swimmer-detection sonars, hand-delivered underwater charges, and marine mammal systems are required in most cases to neutralize an underwater threat. Swimmer-detection sonars typically operate at high frequencies to provide sufficient resolution and are monitored continuously by computer systems programmed to recognize targets and alert duty personnel automatically, while giving them the means to evaluate the situation on geographic displays. Intruders can be called to the surface using hailing systems, and if they fail to comply, attacked with subsurface charges deployed from boats. For detecting and apprehending swimmers, marine mammals are highly effective. For an investment similar to that of a working dog program, sea lions can perform sentry duty, trained to alert on any swimmer and immediately take action to tag and apprehend him. These animals adapt to virtually all climates and are comfortable patrolling in and around piers and ships. They are ideal guards for afloat assets.

Air defense offers a third force protection challenge and is accomplished through participation in a larger air defense network including air traffic control, perimeter air defense systems, and armed aircraft to cover large areas most efficiently. All airspace in the vicinity of protected assets should be monitored. System radars detecting air traffic in these areas can make initial call-ups and dispatch military planes to determine an intruder’s intentions. If these are hostile, air and ground weapons can be used to engage. Difficulties in determining hostile intent and engaging at sufficient range to neutralize an air attacker reduce the applicability of anti-air point defenses at or near the defended submarine. Only a large network with significant detection and communication capabilities can determine hostile intent authoritatively.

Determining Hostile Intent
As noted earlier, deciding to engage depends crucially on solving the difficult problem of determining hostile intent. The issue is further complicated by the location of our submarine bases. If these were in the middle of nowhere, the presence of any outsiders would be suspect, and intruders could be reasonably considered as hostile. For compelling reasons – quality of life, logistics, availability, etc. – submarine bases are co-located with civilian activities. Innocent intruders must be expected, and a local population of civilians increases the risk that an innocent may do something that could be classified as hostile. Reasonable checks on permission-to-fire are required to minimize the chance that a bystander will be injured or killed. Multiple barriers, warning shots, and eyes-on-target are some of the restrictions that may be required in the interest of safety. Normally, a robust system of checks is beyond the capability of the ship’s force alone, validating the requirement for additional shore support as part of a layered defense.

In addition to a formal, integrated force-protection system of systems, commanders must take advantage of every opportunity to increase the terrorist’s problem. Because a terrorist depends on patterns to assess vulnerabilities and craft a workable plan, “varying the routine” has been demonstrated to increase his difficulty significantly. If sentry rounds are random, the terrorist can-not develop a plan to bypass them and must invest resources and effort in attacking them overtly. If Special Forces and/or units from other services use submarine bases frequently for exercises, the terrorist cannot discount the possibility that significant military strength may be present at any time. Using local law enforcement to patrol periodically on base is also an effective force multiplier. These measures are no substitute for robust force protection, but they are simple and inexpensive means to improve its effectiveness.

Continuous Improvement
By its nature, the face of asymmetric warfare changes continuously. More sophisticated weapons will become available as improved military technology proliferates around the world. As homemade explosives get larger, the vehicles that deliver them become more effective. Weapons of opportunity, such as commercial airliners, will always exist and their selection is limited only by the imagination of the terrorist.  Vigilance by civilian law enforcement organizations will mitigate the danger to some extent, but the threat will evolve regardless of their best efforts. Consequently, commanders must keep abreast of terrorist capabilities, tactics, and objectives, and force protection must evolve along with the threat. We need to assume that terrorists have at least the assets available to local criminals and at worst, increasing capabilities with each attack. Realistically, we also need to assume that the terrorist knows yesterday’s changes to our force protection plans and is actively working to subvert them.

Good intelligence is critical but often unreliable. Any prior warning makes self-defense more effective, and an improved posture may deter an attack. But because there is a significant chance that preparations for an attack may have gone undetected, our submarines must be protected 24/7. Substantive intelligence that submarines are being targeted should cause affected submarines to put to sea.

Marine mammals offers detection and interdiction capabilities  beyond those of existing technology.

Everyone’s Concern
Submarines are potential targets, but there are robust and effective security measures in place to protect them. The overt measures discussed in this article – and the covert ones not discussed – are the foundation on which the safety of submarines and their crews depend. Our individual responsibility is to understand and support these measures and carry out specific security duties to the best of our ability. Force Protection is everyone’s concern. Conduct your security watches meticulously. Be proficient on your weapon. Don’t ask for or give exceptions. Remain vigilant. Let’s remain safe!

CAPT Miller is the Deputy Branch Head of the Science and Technology Branch of the OPNAV Submarine Warfare Division and former Commanding Officer of USS Tucson (SSN-770).

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