RunSilent, Run Shallow

Proceedings Magazine - October2018 Vol. 144/10/1,388

By Captain JamesH. Patton Jr., U.S. Navy (Retired)

A great deal has changed since World War II submarine offensivecombat operations and Cold War intelligence, surveillance, and reconnaissance(ISR). Many coastal nations have realized that a few capable nonnuclearsubmarines—preferably air-independent propulsion (AIP) types (sometimesreferred to as “SSPs”) armed with antiship cruise missiles (ASCMs)—offer one ofthe best options to provide credible, economical defense of their territorialwaters.

For countries that can afford them, modern nuclear attack submarinescan operate offensively in littoral waters extremely quietly without beingthreatened by the majority of anti-access/area-denial (A2/AD) defensivemeasures. They can penetrate such barriers essentially at will. A modern SSPcan hunker down at very slow speeds and become nearly impossible to find in aclassic broad-area, passive sonar antisubmarine warfare (ASW) search conductedby an SSN. 

In other words, the defending nation finds it difficult to keepthe offensive SSNs out, but those SSNs cannot find and engage the defensiveAIP/ASCM submarines that are keeping the surface warships and carriers out ofthe A2/AD zone.

What’s a navy to do?

ANew Threat Environment

Althoughthe post–Cold War U.S. surface navy took some time to rediscover the idea offighting in the littorals, submariners never lost sight of it. Deep-ocean Hunt for Red October –type peacetime ASW events drewthe most attention, but the real bread-and-butter operations for U.S.submarines involved covert ISR operations in Soviet coastal waters. ¹ Thishistory of shallow-water ISR extends back as far as the pre–World War II periodwhen U.S. submarines closely watched the Japanese fortification of Pacificislands. During the course of the Pacific war, many offensive submarineoperations were conducted in the shallow waters of the Pacific Rim inside ofwhat is often called “the first island chain.”

The be-all and end-all of the Cold War’s “Third Battle of theAtlantic” (as Professor Owen Cote of the Massachusetts Institute of Technologynamed it) was the United States’ and NATO’s “acoustic advantage.” At times, theadvantage was as great as 40 dB. In practice, this meant U.S. submarines couldhear activity at many tens of miles that the enemy could hear at one mile—anice edge to bring to a fight. That differential no longer exists, and eventhough some edge against potential adversaries’ top-end nuclear and nonnuclearsubmarines remains, it often translates into initial detection ranges measuredin hundreds of yards rather than miles.

The bad news is that modern, quiet submarines no longer have theability to sanitize a given geographic area of other modern, quiet submarines,since the mean time to detect an adversary is unacceptably large, especially inthe littorals—waters shallower (often much shallower) than 100 fathoms, wherebackground noise and extremely quiet propulsion systems combine to make passivesonar less effective than in the open ocean. 

The goodnews, however, is that adversary submarines face the same problem. A Virginia -class submarine can operate with relativeimpunity within a denied area. Improvements in foreign subs mean a Virginia may not be as effective as a U.S. submarineonce would have been at antisubmarine warfare, but it can perform other typesof valuable mischief. 

Successfulsubmarine employment in current and foreseeable scenarios will require a“connectivity advantage” analogous to the Cold War acoustic advantage. The quantity of data passed is less important than the quality of the data—and its assurance throughout asubmarine’s operating envelope—and it will require the ability to disrupt theother side’s connectivity.

TheProblem for Shallow-Water Defenders 

Defensive submarine operations in shallow waters protect adefender’s coastal waters from invasion. This invasion may take the form of anamphibious landing or an attack on national assets from sea-based air power. Inany case, large surface ships and carriers must close the enemy coast.

Submarines playing defense may need to get close enough to thesurface ships to do their own targeting. In World War II, most successfultorpedo attacks were conducted from inside 2,000 yards, but modern torpedoespermit attacks from greater than 20,000 yards. As a rule of thumb, if thesubmarine can see the target, it can be attacked.

Surface ships possess highly developed close-in ASW detectionand engagement capabilities including effective periscope detection radars.This leads to a problem for the defensive submarines. Submarines possess fourcritical core capabilities—stealth, mobility, firepower, and endurance.Nonnuclear submarines—even AIP ones—fall short in terms of mobility andendurance if they must search for and close highly mobile targets such asamphibious ready groups (ARGs) or carrier strike groups (CSGs). 

An appropriate tactic for nonnuclear submarines on theirown—shallow—turf is to stay hidden and not move a lot, especially at noisy highspeed. The concept is suited perfectly to employment of long-range ASCMs: stayin “hide” positions until the attack, move to a launch position, attack, thenquickly return to the hide. The weakness of this practice is that someone elsehas to provide the ASCM-equipped submarine with near-real time targeting data.

TheOffense Does not Have It Easy, Either

For purposes of this discussion, offensive submarine operationsrest on several assumptions. First, the location to be attacked is far from thehomeports of the attacker. Second, the deployed submarines will have to operatewithout logistical support for several months. Third, the waters to beinfiltrated might be extremely cold or extremely warm. And fourth, a timelyresponse is critical. 

Large size and significant power for air conditioning andlife-support equipment greatly enhance the platform’s ability to reach distantwaters, whether arctic or tropic, and remain for extended periods. This helpsexplain a recent trend in nonnuclear submarines designs toward the3,000–3,500-ton displacement range as opposed to approximately 1,000 tons, thestandard just a short time ago. But even the large ones do not compete in allaspects with nuclear submarines.

The core values of stealth, mobility, firepower, and enduranceare most fully embodied in nuclear-powered attack and guided-missile (SSGN)submarines. These boats possess the range to cross oceans and the stealth topenetrate A2/AD defenses.

Even so, the SSNs or SSGNs cannot easily take the fight to thestealthy, hidden AIP submarines. And the defensive submarines pose the last,most potent A2/AD threat to the surface ships that wish to attack the territorythe AIP boat is defending.

Whata Navy Can Do

The threat these unlocated defending submarines pose to surfaceships must be eliminated or at least severely mitigated. The vulnerability liesin the means by which these defenders receive targeting data from nodes onshore. The opening round of offensive ASW actions should be land-attack strikesfrom the SSNs and -SSGNs against these nodes, as well as on targeting assetssuch as over-the-horizon radar sites (including secondary strikes on radarsthat pop up after the primary sites are taken down). In this regard, this“suppression of enemy submarine connectivity” is analogous to the familiar suppressionof enemy air defenses integral to any air campaign. 

It isinteresting, but not entirely surprising, that dependence on connectivity (ormission degradation in the absence of it) varies as a function of submarinetype. That is, the more capably a submarine platform can use mobility and/orendurance to compensate for late or inaccurate intelligence, the less itdepends on off-hull support. Additionally, the bigger a platform is and thegreater discretionary electrical power it has for sensors and computerprocessing of raw data, the more it is likely to become a source for rather than a user of aninformation grid. 

Two key assumptions support the concept that disruptingshore-based targeting facilities and their connectivity to offshore submarines willsubstantially neuter a modern A2/AD complex. The most critical assumption isthat adequate command and control connectivity will be maintained with thepenetrating SSNs and SSGNs. The other is that the defensive submarines largelywill be incapable of effectively operating autonomously because of the largesize of the A2/AD area that results from defending against long-rangeland-attack cruise missiles. 

The U.S. submarine force owns a long history of having tofunction effectively in an independent role with limited means to ask for orreceive guidance from their masters ashore. This has resulted in a necessaryskill set that emphasized the technique—the art—of submarine warfare. Itrequired an extensive apprenticeship to develop. 

Moderntechnology provides very large “pipes” through which to pass two-way data,information, and knowledge. It also enables a more procedural manner ofsubmarine warfare, a tempting scheme for countries with smaller navies.Technology therefore permits these platforms to be effective while manned withless experienced crews—so long as this high bandwidth connectivity is notdisrupted. 

MoreData, More Risk

If highly trained U.S. submarine forces can continue to resistthe temptations associated with having these large pipes available and activelymaintain the techniques required to operate effectively in a degraded command,control, communications, computers, and intelligence environment, then both ofthe above assumptions should remain true.

Offensivelyoriented submarines typically have more options for connectivity due to theirlarger size, available power, and redundancy in equipment. But properly operatedthey should be less dependent on connectivity thansmaller and power-limited defensively oriented submarines. 

This dichotomy provides favorable options for the offensiveplatform and highlights a defensive vulnerability to be exploited—all whileplaying to an offensive strength. Keeping SSPs moving by forcing them to domore of their own ISR and targeting exposes them to the maximum danger from theoffensively minded SSNs and SSGNs while also consuming their limited AIPcapability. Cutting off the data tether to the land increases the chances SSPswill surrender the advantage of silence and make the kind of noise that onlymotion induces. An underwater submarine duel makes for great movies—but it isnot how the Navy will win a submarine battle in the littorals.

1. Asubstantive examination of these operations is contained in Sherry Sontag andChristopher Drew, Blind Man’s Bluff: The Untold Story ofAmerican Submarine Espionage (New York: PublicAffairs, 2016).

CaptainPatton served on two SSBNs and five SSNs, commanding the USS Pargo (SSN-650). He also served in the Office of theCNO in submarine research and development, as the chief staff officer anddeputy for readiness and training at Submarine Development Squadron 12, as thedirector of tactical training at Naval Submarine School, and as the director ofwargaming systems at the Naval War College. He now consults on matters ofstealth warfare, sensors, weapons and communications. He served for three yearsas the technical consultant to Paramount Pictures for the film The Hunt for Red October .