The revolution in naval warfare continues. In fact, the revolution has gone into overdrive in this age of inexpensive, plentiful, lethal drones and guided missiles. The cost of armaments is pivotal. Nowadays it is cheap to threaten an oceangoing navy yet pricey to defend it. Not to mention hazardous. Last week, in fact, an antiship missile lofted seaward by Houthi militants reportedly closed to within a mile of the destroyer USS Gravely before being batted down by the vessel’s close-in weapon system (CIWS), an automated, radar-guided Gatling gun able to disgorge 4,500 projectiles per minute. 

CIWS represents the last line of defense for an American ship of war, and it engages targets at knife-fight range. Surface combatants are equipped with layered defenses able to lash out at hostile ordnance scores of miles away. The farther away, the better. That being the case, it would be imprudent in the extreme to let a threat approach within Gatling-gun range as a matter of tactical choice. No watch officer would make such a choice. If a CIWS intercept takes place too close aboard, in fact, fragments of the missile could pepper the ship. Fragments become shrapnel, and inertia carries them onward toward the ship under fire. 

Point defense, that is, could produce catastrophic success. Thankfully it did not during the Red Sea encounter. 

The sequence of events on board Gravely remains a mystery, and we may never know precisely what happened. In all likelihood navy leaders will withhold details for fear of alerting current or prospective foes to U.S. Navy weaknesses. But we can speculate. Maybe the destroyer fired defensive surface-to-air missiles and the incoming round evaded them. Or the ship may have suffered an equipment fault. Gravely is outfitted with the  Aegis combat system, an integrated radar, computer, and fire-control system that represents the vanguard of shipboard defenses. A breakdown in battle could in effect disarm the vessel’s outer defenses. Or human failings of some sort could account for the last-minute engagement. Mistakes are commonplace in combat, when the stakes are high, time is short, options narrow, and information is incomplete, overabundant, or ambiguous. 

That an outclassed antagonist like the Houthis can menace a dominant navy is nothing new, though. Just ask Julian S. Corbett. A century-plus ago the English naval historian and theorist saw his scheme of naval warfare turned upside down with the debut of newfangled naval weaponry. During his lifetime sea mines and torpedoes superempowered rudimentary submarines and surface patrol craft, letting winsome, lightly armed “flotilla” craft—heretofore an afterthought for battle-fleet commanders—pose a novel and grave danger to battleships, cruisers, and other major surface combatants that ventured within their (generally short) reach. 

For Corbett the revolution in seaborne armaments upended centuries of naval practice, making it hard if not impossible to derive lessons from the past that remained relevant for an age of steam, thick armor, and hard-hitting gunnery. During the age of sail, capital ships fought capital ships. They could ignore lesser enemy ships because they massively outgunned them. That was no longer true by the twentieth century. Perversely, though, the age of sail constituted the only reservoir of historical data for navalists to draw upon. Corbett bewailed how “the whole naval art has suffered a revolution beyond all previous experience,” and opined that it was “possible the old practice is no longer a safe guide.” Or as the historian Theodore Ropp put it, David, in the guise of subs and patrol craft, might not be able to vanquish Goliath, an enemy battle fleet, in an all-out slugfest. But he could make Goliath pay a heavy price for access to near-shore waters—or perhaps deny access altogether. 

The naval revolution has gone ashore since the days of Ropp and Corbett. A sail-driven warship might have been a fool to fight a fort, as Lord Horatio Nelson reputedly quipped (and as the late Captain Wayne Hughes, the dean of fleet tactics and scarcely a lesser personage in naval circles, certainly did, codifying Nelson’s perhaps-apocryphal maxim as one of the “cornerstones” of sea combat). But in Nelson’s day, staying out of range of shore-based antiship weapons was a relatively simple affair. Only small sea areas lay under the shadow of crude, short-range cannon. Ships could outflank forts with relative ease. 

Technology kept effective firing ranges for coastal artillery short until deep into the twentieth century. As military aviation matured, however, shore defenders increasingly wielded the power to strike at fleets moving offshore at distance. Broad sea areas now fell within reach. Precision-guided missiles have only redoubled the striking power of land-based forces, not to mention multiplying the reach of the descendants of Corbett’s superempowered flotilla craft. 

But these are all purely military developments concerning the balance between waterborne- and land-based sea power. Strangely, though, the price of shipboard defense has become a factor of colossal moment in naval warfare. Corbett, who lived before the era of ultra-high-tech weaponry, never could have foreseen how the cost of ammunition would distort tactics, operations, and even strategy. He was chiefly worried about perpetuating the Royal Navy’s status as the world’s premier seagoing fighting force. Ships were expensive in his lifetime, when armored dreadnoughts were the coin of the realm in naval warfare. The historian fretted at the expense of constructing and operating capital ships. But gun ordnance was cheap. It was affordable in bulk to stock the magazines of British men-of-war. Accordingly, ammunition costs were an afterthought for Corbett and kindred naval pundits. 

No longer. Nowadays ordnance is beyond pricey. Because of its complexity, and because of fitful demand from peacetime navies, industry struggles to manufacture precision munitions in large numbers and with dispatch. A few years ago the doughty scribes at The Warzone tallied up the per-unit cost for ship-launched U.S. Navy missiles, mainly from the venerable Standard Missile (SM) family. Thus far the weapon of choice in the Red Sea has been the latest variant of the SM-2, which rings in at just under $2.4 million per round. An SM-6, a “bird” featuring surface-to-surface as well as surface-to-air capabilities, tops $4.3 million per copy. An SM-3 ballistic-missile interceptor will set you back a whopping $36 million. Whichever weapon a ship’s combat team selects, that’s quite the price tag to bring down a drone or repurposed missile that costs Houthis or their Iranian patrons thousands of dollars to field. 

Navy chieftains now confront an unsettling differential equation: the U.S. Navy is expending scarce missiles at a quicker rate than defense budgets are funding new copies, and quicker than weapons makers can assemble replacements. Operations against Houthis, however necessary—freedom of the sea is an invaluable public good—could drain a finite inventory of armaments that could be needed in more critical theaters. Theaters such as the Western Pacific, where the Pentagon regards the People’s Republic of China as the foremost challenge, or around Europe’s aquatic periphery, where Russia poses a challenge of lesser but still worrisome magnitude. 

In other words, the more ordnance expended in the Middle East, a theater of secondary importance to U.S. national interests, the less available to Eurasia’s east and west, theaters commanding utmost importance. That could be a difference-maker. Persevering with the current ordnance-intensive approach off Yemen could have repercussions of strategic import. How can the Pentagon and the U.S. Navy escape the remorseless logic of steep costs, constrained industrial capacity, and the consequent drawdown of the maritime armory? 

Four basic ideas to that end. The first two are human in nature and—theoretically, at least—soluble in fairly short order. One, restore the primacy of strategic thought within the U.S. national-security apparatus. No nation can afford to define every commitment, everywhere on the map, as a top priority warranting maximum expenditure of resources for an indefinite period of time. And yet that is the tendency for global powers like the United States. 

At its most fundamental, strategy is about setting and enforcing priorities. If the U.S. military spends martial resources too lavishly in the Red Sea, it will place what matters most in jeopardy for the sake of something that matters less. That would be gross strategic indiscipline, and it would court disaster. 

Two, get allies and partners to take partial ownership of the problem. Freedom of the sea is a common trust of all seafaring nations; all seafaring nations are its beneficiaries and custodians, and they should help protect it. In fact, they have to or suffer the economic consequences. U.S. emissaries should impress upon allies, partners, and friends that the Red Sea and Middle East inhabit a region of middling importance to the United States. That being the case, the region merits middling expenditures of U.S. resources, and on a not-to-interfere basis with higher priorities in East Asia and Europe. Others have to take up the slack. Or not. 

If fellow seagoing societies are so apathetic about nautical freedom that they can’t be bothered to guard it—if they’re willing to let Houthi attacks convert the Red Sea into a dead sea for merchant shipping—then it may be time for Americans to shrug.