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What a drag. Top Gun was about the best of the best flitting around the skies, kept aloft by a lonely impulse of delight. This list of History's Worst 5 Submarines catalogues the worst of the worst lumbering around in the briny deep. Such a vessel is a millstone dragging down the fortunes of its navy, its parent military, or the society that puts it to sea.

Call it Bottom Gun.

Now, it's possible to rank hardware, including submersibles and their armament, purely by technical characteristics. The crummiest piece of kit -- condemned by shoddy design, faulty construction work, or premature obsolescence -- is the bottom-feeder on such a list. In the case of submarines, then, tallying up speed, submerged endurance, acoustic properties, and kindred statistics offers a reputable way to proceed. But it tells only part of the story.

Carl von Clausewitz, that doughty purveyor of strategic wisdom, helps reveal the rest. Clausewitz defines strength as a product of force and resolve, affirming that people -- not machines -- compete for supremacy. The weapon or platform is just an implement. Both material and human factors, consequently, are crucial to success in strategic competition or war. You can't judge the best of the best or the worst of the worst by widgets alone.

Depicting strength as a multiple rather than a sum makes intuitive sense, doesn't it? If either variable is zero -- if hardware or seafarers are worthless -- a boat supplies zero strength to its parent fleet. The finest crewmen in the world stand little chance if their boat is hopelessly outclassed technologically, if its weaponry malfunctions, or if the navy skimps on maintenance, overhauls, or logistical support. "Damn the torpedoes!" exclaimed Lieutenant Commander Dudley "Mush" Morton, one of history's greatest undersea marksmen, after his Wahoo discharged a volley of nine Mark XIV torpedoes against a Japanese convoy -- only to see every "fish" miss or malfunction.

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Skill and élan go only so far toward overcoming a material deficit.

Or, conversely, a submarine boasting the latest in technological wizardry accomplishes little if handled by an incompetent or apathetic crew. There's a good reason  a ship, its crew, and its commander are all known by the ship's name. The relationship between man and materiel is symbiotic. The hull provides a home and sustains life, while the mariners manning the hull provide seamanship and upkeep and fight the ship when need be.

Senior leadership is crucial to the silent service, even more than in surface fleets. Subs operate largely independently, free of micromanagement from on high. In effect a boat takes on the personality of its skipper. A boat blessed with a skilled, aggressive commander like Mush Morton or Eugene Fluckey is an effective boat. A sub not so blessed is apt to run afoul of hard luck--or worse.

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Despite submariners' penchant for independence, though, higher-ups can handicap their performance indirectly. Navies are bureaucracies, and they shape minds. Officialdom rewards officers who comply with established practices while punishing those who flout routine. If top leaders embrace methods that defy tactical reality, they can negate much of a submarine's potential. Its combat power misapplied, it degenerates into a wasting asset.

Either inert materiel or inert people, it seems, reduce a boat's real-life combat power--regardless of how impressive its technical specifications look in Jane's Fighting Ships.

Worse still, an ineffective submarine can actually subtract from its navy's strategic efficacy. Henry Kissinger observes that deterrence is a product not just of Clausewitzian strength but of an adversary's belief in that strength. In all likelihood, that is, an adversary who doubts another's physical capacity or resolve to follow through on a threat will not be deterred. The same goes for coercion. No one does an antagonist's bidding at gunpoint if the gunman's sidearm appears rusty or his hand quavers.

A sad-sack boat's performance, then, can detract from a navy's renown for prowess beneath the waves--undermining national leaders' efforts to deter or compel rivals.

And lastly, building submarines, of the nuclear-powered variety in particular, imposes heavy opportunity costs on a navy. Money spent on nuclear-powered attack or ballistic-missile subs (SSNs and SSBNs, respectively) is money that can't be spent on surface combatants, amphibious-assault ships, and other workhorse platforms. Overall fleet numbers may suffer for the sake of undersea warfare.

And indeed, at present the U.S. and Royal navies are struggling with the cost of fielding replacements to their Trident SSBNs. SSBN programs could crowd out other shipbuilding priorities, leaving behind boutique navies comprising too few assets for commanders or statesmen to risk in battle. Here again, the credibility of a nation's bareknuckles diplomacy could turn on innate features of submarines. Too expensive a boat is a bad boat.

Factoring in all of this, here's how to rate history's worst submarines. One, did a sub's basic design, the quality of its construction, or its expense cancel out whatever tactical or operational promise it held? Two, did its crew egregiously fail to execute assigned duties, whether out of incompetence, carelessness, or faulty doctrine or tactics? And three, was its performance so deficient that it set back national power or purposes?

A boat -- or group thereof -- that meets these standards warrants membership in an undersea hall of shame. Herewith, History's Worst 5 Submarines, listed from least bad to worst of the worst:

5. Thresher, Scorpion, and Kursk

Why the hodgepodge? These are boats that sank under puzzling circumstances, damaging a great-power navy's reputation for excellence at a time when reputation truly mattered. Because it's hard to say for sure what happened -- whether equipment or human failure was more blameworthy -- these disparate boats belong in a class of their own.

Thresher, the lead boat in a new class of American SSNs, suffered catastrophic flooding in April 1963 while operating near its maximum operating depth. Deep water means intense pressure. Even a small leak in a piping system can quickly outstrip damage-control teams' efforts to patch it. Speculation has it that a weld sprung a leak, shorting out electrical equipment and causing a reactor scram. Cascading failures kept the boat from surfacing. But as Admiral Hyman G. Rickover, the godfather of U.S. naval nuclear propulsion, told Congress, "the known facts" about the disaster "are so meager it is almost impossible to tell what was happening aboard Thresher."

What we do know is that the accident sent the U.S. Navy scurrying for answers -- and trying to mend the silent service's esteem -- at a critical juncture in the Cold War. The Cuban Missile Crisis was a recent memory, while Admiral Sergei Gorshkov's Soviet Navy was embarking on a crash buildup. Clausewitz portrays military competition as a "trial of moral and physical forces" -- of strength, on other words -- "through the medium of the latter." The death of Thresher worked against the idea of U.S. undersea mastery -- heartening Moscow for the zero-sum contest between East and West.

Another American boat, the Skipjack-class SSN Scorpion, went down in May 1968. Again, courts of inquiry were unable to determine for sure what had happened. The Naval History and Heritage Command, however, reports that "the most probable event was the inadvertent activation of a Mark 37 torpedo during an inspection." The fish either commenced running within its tube, or was released, circled around, and targeted Scorpion. Either way, the cataclysm applied another sharp blow to the submarine force's prestige. The balance of moral forces again tilted Moscow's way.

Built after the Cold War, Kursk, an Oscar II-class sub, became a metaphor for the economic and political woes that ailed post-Soviet Russia. Many Russians, including President Vladimir Putin, bewailed the downfall of the Soviet Union. They longed for the days when their country was a superpower. That the Russian Navy still operated a potent undersea fleet was a token of past dignity and hopes for a restoration. Those hopes took a hit in 2000, when a torpedo malfunctioned -- setting off a chain reaction of explosions that left the pride of the Northern Fleet at the bottom of the Baltic Sea.

The lesson from these sinkings and similar debacles--think last year's explosion on board the Indian diesel boat Sindhurakshak--is sobering for navies. When a ship becomes a symbol, its death has outsized political and even cultural ramifications. Failures in seamanship or everyday routine, then, can reverberate far beyond a boat's hull.

4. Type 092 Xia

You can say one good thing about the next boat on the list: it hasn't sunk. On the other hand, China's first SSBN has done little to advance its chief mission, nuclear deterrence. The lone Xia entered service in 1983. Its crew finally managed to test-fire an intermediate-range JL-1 ballistic missile in 1988, overcoming debilitating fire-control problems. Yet the boat has never made a deterrent patrol and seldom leaves the pier. Retired submarine commander William Murray describes the Xia -- and the Han SSNs from which its design derives -- as "aging, noisy, and obsolete."

American submariners joke that some foreign subs are as noisy as two skeletons making love inside a metal trash can. When a boat becomes an object of fun, its parent navy has problems. Small wonder China's naval leadership skipped on to a more modern design, the Type 094 -- leaving the Xia a ship class of one.

3. K-class submarines

When new technologies appear, navies habitually deploy them as fleet auxiliaries -- that is, to help the existing fleet do what it's already doing, except better. Undersea craft were no exception a century ago, when navies were still experimenting with them. The Royal Navy's World War I-era K-class boat was a failed experiment, as the nicknames affixed to it--Kalamity, or Katastrophe--attest.

Designed in 1913, these boats were meant to range ahead of the surface fleet, screening the fleet's battlewagons and battlecruisers against enemy torpedo craft. Or they could seize the offensive, softening up the enemy battle line before the decisive fleet encounter. A solid concept. But to keep up with surface men-of-war, such a boat would need to travel at around 21 knots on the surface, faster than any British sub yet built. Diesel engines were incapable of driving a boat through the water at such velocity. The Admiralty's speed requirement, therefore, demanded steam propulsion.

However sound the tactics behind the K-class, outfitting subs with steam plants was a bad idea. Ask any marine engineer. Boilers gulp in air, they generate prodigious amounts of heat, and they emit exhaust gases in large quantities. Trying to submerge a steamship, consequently, means trying to submerge a hull with lots of intakes and smokestacks. Unsurprisingly, the K-class leaked. The heat was torrid while underwater. It wallowed in rough seas, and displayed a troublesome reluctance to pull out of a dive. Of 18 K-class boats, none was lost to enemy action. But six -- a full third of the class -- were lost to accidents.

The most gallant, astute crew can achieve little with hardware that is backward. Never again did the Royal Navy establishment foist a conventional steam-powered boat on British tars.

2. K-219. This Yankee-class Soviet SSBN suffered an explosion and fire in a missile tube in 1986, while cruising some 600 miles east of Bermuda. It occupies an ignominious place on this list because of the repercussions of losing a ballistic-missile boat -- a vessel stuffed with nuclear firepower -- and because by most accounts the mishap was needless. Here, as with the travails of the K-class boats, blame lies at the feet of obtuse senior leaders. Such failings annul even capable platforms.

Two expert commentators, Igor Kurdin and Wayne Grasdock, explain why. First, the Soviet leadership had set the SSBN force on a helter-skelter patrol schedule to reciprocate as the Reagan administration deployed the Pershing II and cruise missiles in Europe. Crew training and periodic overhauls slipped as Soviet SSBNs made two or three deterrent patrols each year, well beyond their usual clip. Massive turnover within K-219's crew helped little. Performance suffered as the boat prowled patrol grounds far from Soviet bases and shipyards.

Kurdin and Grasdock observe, second, that the Soviet Navy was lackadaisical about safety by comparison with the U.S. Navy. (To its credit, the U.S. silent service got religion in the wake of the Thresher and Scorpion incidents, instituting its SUBSAFE program.) Evidently, they write, the explosion and fire may not have occurred "if one more person had checked the last maintenance performed on missile tube No. 6." In short, to keep up appearances in the late Cold War, Moscow and the naval establishment imposed an operational tempo on the SSBN force that prompted submariners to cut corners on basic standards.

The result: a black eye for the Soviet Union, a superpower in retreat. Here again, neglect of the fundamentals had major political import.

1. Imperial Japanese Navy submarine force. Granted, it seems unfair to indict an entire silent service on this list. But what did IJN submarines accomplish against the U.S. Pacific Fleet during World War II, when the American war effort depended on long, distended sea lanes vulnerable to undersea assault? Not much. Subpar performance resulted not from a shortage of capable boats or skillful, resolute sailors -- by most accounts Japanese fleet boats were the equals of the Gato-class boats that spearheaded the U.S. submarine campaign--but from a shortage of flexibility and imagination among top commanders.

As noted before, navies tend to use unfamiliar technologies as auxiliaries. So it was with Japan. But whereas some services innovate over time, the IJN leadership proved stubbornly shortsighted. For decades, commanders had marinated themselves in a bowdlerized version of Alfred Thayer Mahan's works. In particular, they made a fetish of Mahan's advocacy of duels between big-gun warships. Having donned doctrinal blinkers, they could conceive of few ways to employ subs beyond supporting the battle fleet. Rather than inflict mayhem on U.S. logistics--much as the German Navy did in the Atlantic, and much as the U.S. Navy did against Japanese sea lanes in the Western Pacific--the IJN allowed transports, tankers, and other vital but unsexy shipping to pass to and fro unmolested. Vast quantities of American war materiel traversed the broad Pacific--letting American forces surmount the tyranny of distance.

Inaction added up to a colossal missed opportunity for Imperial Japan. The IJN had largely mastered the aerial dimension of naval warfare, putting to sea impressive aircraft-carrier task forces. Pearl Harbor bore witness to Japanese carrier aviators' prowess. Why its backward approach to submarine warfare? For one thing, there was no Isoroku Yamamoto of undersea combat. Admiral Yamamoto threw his immense personal prestige behind the strike on Oahu, threatening to resign if top commanders rebuffed the aviation-centric strategy he proposed in favor of battleship engagements. The submarine force had no such champion to challenge orthodoxy. The IJN, accordingly, clung to its quasi-Mahanian dogma throughout the Pacific War. A potent submarine force ended up being a wasting asset, consuming resources for little reason.

For which U.S. military veterans everywhere are eternally grateful. When shipping out for oceanic battlegrounds, it's good to face history's worst subs. The Imperial Japanese Navy submarine force is hereby designated Bottom Gun.