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."