IT’S EASY to forget the virtues of submarines, which lurk beneath not only the waters but also the consciousness of most Americans. They aren’t as iconic as fighter jets or as visceral as tanks. But they can deny a stronger enemy navy control of important waters. Afterward they can exercise command of the sea, blockading or projecting power onto enemy shores with impunity. These elusive warships, in other words, pack an outsized punch.
Just ask Eugene Fluckey. Nicknamed “Lucky Fluckey,” the World War II submarine commander sent the most enemy tonnage to the ocean’s bottom of any skipper in the Pacific. Sinking Japanese tankers, freighters and other merchantmen dismembered a Japanese Empire reliant on sea transport. And raiding shipping was an option of first resort for Washington. U.S. Pacific Fleet submarines were able to start attacking Japanese shipping while American battleships were still burning in Pearl Harbor—long before the U.S. Navy surface fleet penetrated western Pacific waters. That’s what naval specialists call “sea denial.” It’s a strategy for hindering or preventing stronger adversaries from using certain nautical expanses.
Submarine operations spread progressively westward as the navy seized Pacific islands where forward bases could be built. Nearby bases let U.S. submariners establish a near-constant presence in Asian seas, sinking even more merchant shipping while pummeling the Imperial Japanese Navy from below. As the tide turned in the Pacific, undersea warfare made an indispensable contribution to American “command of the sea,” meaning near-total control of important sea areas.
And late in the war, Fluckey’s boat USS Barb took the fight directly to Japan, engaging in gun duels against Japanese shore sites. A landing party even went ashore to blow up a train. Such theatrics aside, Harvard professor Stephen Rosen maintains that a submarine blockade of Japan could have compelled Tokyo to surrender—even had President Harry Truman declined to order the atomic bombings of Hiroshima and Nagasaki. That’s high praise for these humble-looking ships of war.
Sea denial, sea command, the exploitation of command: submarine operations span the range of naval missions. Yet despite a century’s proof of submarines’ efficacy, from World War I in the Atlantic to the competition with China today, the classics of sea-power theory—the closest thing seafarers have to a how-to manual of naval combat—are puzzlingly silent on how to employ them in wartime or peacetime. The classics concentrate overwhelmingly on surface warfare, scanting undersea combat. It is high time to bring submarines into the canon.
AS AMERICAN submariners like to boast, some ships are built to submerge while others are made to submerge—once! There’s truth to that jest. First, these are warships that operate in three, not two, dimensions. In this sense they resemble combat aircraft, which can overfly surface fleets at altitudes of their choice. Adding that z-axis to submarines’ maneuvering space lets them operate not just near but also within the defensive perimeters around enemy formations. Think about the German U-boat lurking underneath a U.S. Navy destroyer in the World War II film The Enemy Below .
Surface vessels navigate across what amounts to a featureless plain, whereas submarines roam within a vast, three-dimensional column of water. This flexibility opens up tactical and operational vistas for submarine skippers that are unavailable to their surface brethren, whose ships lumber around in (mostly) plain sight. On the other hand, sub crews have to contend with terrain when operating in shallow water. Undersea warfare resembles land warfare in that sense. Soldiers work around mountains, valleys and defiles. Submariners must take account of the sea floor’s uneven if not shifting topography—in the near-shore environment in particular.
Second, concealment is a submarine’s chief method of defense. Surface-ship designers assume adversaries can detect, target and attack men-of-war plying the ocean’s surface. Such vessels must be stoutly built to absorb hits from enemy missiles or gunfire. They also boast elaborate active defenses—radar, antiaircraft and antiship missiles, electronic warfare—to ward off assault. The overriding assumption: ships exposed to enemy sensors will take hits.
By contrast, submariners go to extravagant lengths to hide. Loath to give away their presence—and thereby compromise their defenses—submariners typically operate their sonar sets in “passive” mode. They listen for telltale sounds emanating from enemy boats. Once they hear another ship’s engineering plant or other noise, they can identify, track and target it. This acoustic cat-and-mouse game works both ways. Running silent helps a boat evade detection. Slowing to a crawl quiets noise from the propulsion machinery.
Third, submarines are loners for the most part. Surface engagements are about concentrating firepower at decisive places on the map to overwhelm an opponent. Submarine warfare is about individual units hunting for action. Surface ships generally steam in concentric formations centered around “high-value units” such as aircraft carriers or amphibious transports. Outlying picket ships guard the high-value unit against surface, aerial or subsurface assault. A layered defense constitutes the carrier’s best chance of survival in a contested environment. Once in range, the formation projects offensive firepower against a hostile fleet or onto hostile shores.
By contrast, the submarine’s operating characteristics and need to remain unseen make independent operations its prime mode of action. Communicating with fellow boats increases the dangers of detection, as does operating in packs with them. Plus, passive detection represents a submarine’s best way to find adversary shipping. Passive sonar works best at low speeds, when the sub makes little noise of its own to obscure sounds emanating from an opponent. Sprinting short distances and pausing to listen is one tactic. Trailing a towed-array sonar—a “tail” festooned with hydrophones—behind the boat is another. A towed array lets crews hear minute sounds with even less interference from their own machinery.
While navies sometimes attach submarines to surface task groups, turning them loose in the depths remains the best way to prosecute undersea warfare. Freedom of action boosts an entrepreneurial crew’s chances of staying hidden, of finding enemy ships in the briny deep or on the surface, and of striking hard should circumstances warrant. Independence thus magnifies their combat potential. These disparities—technology, the radically different setting, this proclivity for stealth—add up to an approach to sea combat so different from surface warfare that it merits a fresh look. Sea-power theory schools judgment—and can improve the practice of undersea operations.