Factor in such disproportionate expenditures and the margin between U.S. and foreign spending doesn’t gape nearly so wide as budgeteering implies.

The walking dead are ravaging Capitol Hill—again! I refer not to literal ghouls but to misleading ideas about navies that refuse to die in policymaking circles. The living dead shamble around during election season or just after—in other words, at times of political flux like this one, when one house of Congress has changed hands and the other is undergoing a leadership shakeup.

(This first appeared several months ago.)

Take out one zombie factoid with a shot to the head and ten or a hundred more just like it trample the fallen corpse to get at you.

The latest to traffic in undead ideas is Sen. David Perdue, representing my erstwhile home state of Georgia. He’s taking over as chairman of the Seapower Subcommittee, an arm of the U.S. Senate Armed Services Committee. The new chairman exhibits a gratifying sense of urgency about America’s return to history after its post–Cold War strategic holiday, and about the need to bulk up the sea services to wage protracted strategic competitions against peer competitors.

That’s the good news. In stating his case, though, Senator Perdue uttered a factoid that is as manifestly incomplete as it is commonplace as an index of naval power. “Today we have the smallest Army since WWII, the smallest Navy since WWI, and the oldest and smallest Air Force ever,” he told Defense News. “At the same time, we face complex threats from China, North Korea, Russia, and Iran.”

That’s a dark picture to paint, and Perdue is correct in a strict factual sense: at 287-odd ships, there are fewer vessels in the U.S. Navy inventory now than at any time since the Great War. (Actually, the inventory has rebounded after bottoming out in the 270s—but only by a handful of vessels.) But the important question is whether the navy is powerful enough to accomplish the goals assigned it by senior commanders and their political masters. Naval power is not solely a function of hulls in the water. Think of ships as delivery vehicles. They deliver combat power to a particular scene of action at a particular time, in concert with friendly sea, ground, and air forces, to overcome the combat power a particular foe has staged there.

If the U.S. and allied force outguns the antagonist at the decisive place and time, it is sufficient regardless of how many or few ships take part in the engagement. If not, then U.S. naval commanders have a problem. So we should divorce calculations of naval might from brute numbers of hulls, which reveal little about whether a given fleet size is adequate to apply enough combat power at likely hotspots to fulfill U.S. strategic goals.

What U.S. maritime strategy calls on the navy to do matters a great deal to this calculus. For instance, a 287-ship force might well suffice to mount a hemispheric defense of the Americas, working alongside allied forces from Canada and Latin America. It would probably boast surplus capacity for such humble duty. Yet a fleet that size might be woefully understrength to take the fight to China in the South China Sea, Russia in the Black Sea, or Iran in the Persian Gulf. In short, reaching back to World War I to compare raw numbers reveals little about the outcomes of probable encounters in the here and now, and thus about the prospects for U.S. tactical, operational, and strategic success or failure.

Tallying up ship numbers, then, makes poor shorthand for U.S. naval power. Bean counting yields one datapoint, albeit an important one. There is some bare minimum of assets needed to concentrate strength at scenes of battle. But bean counting not only disregards the enemy, the surroundings, and the goals set by the navy’s overseers, it doesn’t differentiate among ship types. A century ago a battleship counted as a ship of war, and so did a winsome destroyer. A fleet made up entirely of battleships would have been the same as a fleet composed of destroyers by Perdue’s standard. It would have been an entirely different creature.

Today, similarly, a nuclear-powered aircraft carrier bearing scores of warplanes counts as a ship. But so does a littoral combat ship with light armament and one-thirtieth the flattop’s tonnage. So does a lumbering amphibious assault ship that deposits marines and cargo on embattled shores rather than assail enemy fleets. Simple ship counts obscure elementary distinctions like these while making no judgment about the balance among ship types and missions within the fleet.

Statistics can lie. If you couple the “smallest navy since World War I” talking point with the results of realistic wargames showing that the U.S. Navy fields too few vessels vis-à-vis prospective foes under realistic circumstances, though, then you have the makings of a useful benchmark to gauge whether U.S. naval means are sufficient to advance U.S. strategic and political ends. And in turn you can bellow forth a rallying cry to lawmakers, administration officials, and the electorate to furnish more shipbuilding resources.

Apart from gamesters, you can consult scholarly work for informed opinion about these matters. For instance, back in 2010 a team of scribes from the Center for Naval Analyses compiled a study postulating that the U.S. Navy stood at a force-structure “tipping point” beneath which it would no longer be the globetrotting service it has been since Congress passed and Franklin Roosevelt signed the Two-Ocean Navy Act of 1940.

If the sea service dwindled much further in numbers and especially in capability, maintained the CNA team, it would possess too few assets to discharge the missions entrusted to it. The U.S. Navy would revert to the regional force it was before World War II.

The fleet still hovers around that tipping point nine years hence. At least Senator Perdue errs in the right direction by fretting over fleet numbers. In all likelihood the U.S. Navy is too small, even when you redefine ships as delivery vehicles for combat power and estimate U.S. battle strength through that unorthodox but illuminating technique. Still, friends of American sea power need more than soundbites to lend punch to their pleas for a larger fleet.

Now, so as not to pick on Senator Perdue too much, it’s worth noting that the World War I comparison is far from the most loathsome zombie to stampede through force-structure debates at times of political change. However flawed, Perdue’s talking point at least alerts Washington and the nation to danger. Taking other ubiquitous factoids at face value could induce America to relax its guard at a time when relaxing is the last thing it should do.

Two such fallacies come to mind. One holds that the U.S. Navy is “larger” than the next X navies combined, X usually being some double-digit number. That being the case, it should smash smaller rivals into kindling with ease, right? But this factoid makes no sense whatever when cross-referenced against numbers of hulls. Reputable estimates indicate, for instance, that China’s navy will boast over 500 vessels by 2030, even as the U.S. Navy struggles to field a 355-ship fleet. How could America’s navy constitute the larger force?

It turns out that this living-dead factoid refers to the total tonnage of the U.S. Navy fleet vis-à-vis foreign navies. On average American ships displace—or, roughly speaking, weigh—more than their counterparts overseas. Like numbers of hulls, tonnage is not a meaningless figure. Larger vessels can carry more fuel, armaments, and stores. Bigger is better—to a point.

But aggregate tonnage must also be taken in context. For one thing, the size of a ship says little about the armament and sensors installed aboard. A mammoth vessel could bear minimal armament. Combat logistics ships—transports for fuel, ammunition, refrigerated stores, and the like—are a case in point. Undefended by escort vessels, a large ship can make easy pickings for a much smaller foe such as China’s fleet-footed Type 022 Houbei catamarans. These lightweight 225-ton craft pack a heavy wallop in the form of eight anti-ship missiles. Offensive power need not correlate with tonnage, in other words.

For another, U.S. Navy men-of-war must carry more supplies than probable adversaries. After all, likely battlegrounds lie thousands of miles from North American shores. U.S. expeditionary forces must haul everything they need to fight in a China’s, Russia’s, or Iran’s backyard, or they may as well stay home. Meanwhile local defenders may get away with smaller vessels because they operate close to home—near their supply and operational bases—and because they’re backed by the combined firepower of shore-based air and missile forces. Antagonists, in other words, might make do with lesser craft and still attain their goals. The Type 022 is not a war-winning craft on its own. It is a formidable craft when integrated into a defensive thicket made up of ships and shore-based weaponry.

It’s a fallacy, then, to compare the tonnages of U.S. and foreign navies and conclude the battle result is a foregone conclusion. Doing so oversimplifies radically. In reality the bulkier U.S. Navy will square off not against a hostile navy but against a hostile joint force—a composite of sea, air, and ground forces operating close to home. In warfare as in sports, the advantage goes to the team making a home stand. Girth is no guarantee of victory for the visitors.