Virginia-class boats a year. To supply Australia, it needs to raise output to about 2.33 boats a year. In fact, it manages barely 1.1-1.2 Virginias a year, in addition to one Columbia-class SSBN (a bigger vessel capable of launching long-range nuclear missiles) to replace ageing Ohio-class subs. America’s submarine fleet has shrunk from 70-odd boats a decade ago to 67 today—49 SSNs, 14 SSBNs and 4 SSGNs (mid-sized subs capable of firing guided missiles). It will shrink further, to 63, before in theory growing to 66 by 2054. That will still be well short of the navy’s goal of 66 ssns alone. Worse, an agonising maintenance backlog means a third of SSNs are in maintenance or idle. The USS Boise has been out of action for so long—it was tied up in 2017—that the Pentagon this year decided to decommission it. A new dry dock is under construction in Pearl Harbour in Hawaii to speed up maintenance and repair from next year. Even so, regular “depot” maintenance can take over 18 months. The yard’s wartime feats—it put the USS Yorktown, a badly damaged aircraft-carrier, back to sea in three days to fight the battle of Midway in 1942—are a fading memory. Britain, too, is struggling. A parliamentary report warned last month that “shortcomings and failings”, including delays in upgrading the “depleted submarine industrial base”, risked holding up AUKUS, “with serious consequences both for UK national security and for credibility with AUKUS partners”. Unnerved Australian experts are debating options for “Plan B”. Meanwhile, satellite imagery suggests China has been managing to build two attack subs and an ssbn a year since 2024, thanks to expanded facilities at Huludao on the Bohai Sea, says the International Institute for Strategic Studies, a think-tank in London. Nuclear-powered submarines are so expensive and difficult to make—a Virginia-class boat costs about $5bn apiece—because they must keep sailors alive in extreme conditions. Their hulls must be made of special steel that is strong, tough and ductile, and sealed only by expert welders. Controlling buoyancy is tricky: a submarine shrinks as it dives, displacing less water, and so sinking ever faster (and vice versa as it rises). Uncontrolled by ballast and trim, it will either drop to the sea floor (and perhaps be crushed) or bob to the surface. Then there is the problem of propulsion. Submarines of the first and second world war used a combination of diesel engines, to sail on

the surface and charge batteries, and an electric motor for short bursts under water. Nuclear propulsion was a game-changer. “Our submarines have 30 years of fuel or more on board, so effectively, unlimited endurance,” explains Rear Admiral Christopher Cavanaugh, commander of the Pacific Fleet’s submarine forces. “That also gives them stealth. They don’t need to come up and snorkel.” America’s first nuclear-powered submarine, USS Nautilus, made the first journey under the Arctic ice-cap in 1958. In April HMS Vanguard, a British SSBN, completed a record 205-day patrol. On the Annapolis, crews are away for so long they must tell superiors whether they wish to receive bad news from home while at sea. To maintain circadian rhythms, lighting levels follow the day-night cycle of Guam. Cribbage and books help pass the time. Tom Clancy’s “Hunt for Red October” is a favourite. Water quickly absorbs most light and radio waves, which makes submarines stealthy but hard to communicate with. Water readily transmits sound, however, be it the songs of whales or the thrumming propeller of an enemy vessel. The submariner’s art is to understand the layers of temperature and

salinity, the vagaries of the seafloor and current, knowing where to hide and where to find “sound tunnels” to detect faraway objects. You could shout at the top of your lungs and scarcely be heard outside a modern submarine. That is because decks, and the machines on them, float on sound-absorbing “rafts”. The boat’s exterior is covered with a rubber-like coating to further muffle noise and confound sonar. The control room of the Annapolis is a hubbub of loud commands and responses; the cramped torpedo room even more so. Before pulling a brass lever to fire a “water slug” (a blank torpedo), your correspondent had to don earmuffs. But interior noise is most dangerous if there is an “acoustic short”, when a stray object touches both a raft and the outer hull, transmitting sound to the water. Officers prowl the boat looking for carelessly secured equipment or, say, tins of food stored in inviting but forbidden gaps. Pearl Harbour, home to America’s Pacific Fleet, is dotted with memorials— not just to those who died in Japan’s attack in 1941, but also to the submarine crews that held the line thereafter, as the fleet was rebuilt. Unrestricted warfare against Japanese merchant ships in the Pacific, announced within hours of the attack, had greater success throttling Japan than Nazi Germany’s U-boats managed against Britain. Submarines sank about 55% of Japanese vessels lost during the war, including eight aircraft- carriers. China worries that American submarines could unleash similar havoc today. About 80% of its oil imports pass through the Strait of Malacca. Iran’s closure of the Strait of Hormuz, which has caused a global energy crisis, is a salutary warning. There are lessons for America, too. Its bases and other fixed targets, including radars and parked aircraft, have proved vulnerable to Iranian missiles and drones. China’s missile force is formidable, able to rain munitions not only on American bases on the “first island chain”, which runs from Japan to Malaysia (see map), but also with lesser intensity on rear bases in Guam, Hawaii and Alaska. It can also take aim at warships racing across the Pacific to join the fight.

If Chinese submarines can slip undetected through the passages of the first island chain into the Pacific beyond, then American forces would face the additional threat of volleys of cruise missiles fired from any direction. A related worry is that Russia is increasingly making common cause with China. Their submarines conducted joint exercises last year. North Korea’s navy, too, seems to have obtained Russian assistance with its own submarine programme. Even if they don’t join the fighting, Russian and North Korean forces could cause trouble in a Sino-American war simply by going on exercise. All this could stretch America’s submarine force desperately thin. At the least, a credible Chinese submarine threat would slow American reinforcements, giving Chinese forces more time to subdue Taiwan, say. The more American submarines are diverted to hunting Chinese ones, or tracking rival forces, the fewer will be available to challenge a Chinese armada crossing the Taiwan Strait. China still worries about the “open door” America enjoys under water, says Ryan Martinson of the China Maritime Studies Institute at America’s Naval War College. Internal Chinese military writings argue that America’s underwater surveillance system—including satellites, sensors on aircraft and submarines—gives it an “extremely high” chance of detecting Chinese

submarines as they leave port and a “fairly high” chance of intercepting them in the South and East China Seas. One response has been to make its subs harder to detect. The Type 093B SSGNs it now deploys use pump-jet propulsion, like America’s Virginia class, which is quieter than propellers. The bigger Type 095, which may soon undergo sea trials, also seems to use a pump-jet, as well as a more manoeuvrable X-shaped rudder. Yet another new model, the Type 096 SSBN, is under construction. Admiral Brookes says these submarines display “substantial advancements” in nuclear technology, sensors, weapons and noise-quieting—though how advanced is still unclear. Another Chinese strategy is to make the seas less opaque. The “underwater Great Wall” involves a range of systems from sea-floor sensors to satellite observation. Among other things, these create protected “bastions” from which China’s SSBNs can fire nuclear weapons at most of the American mainland. American commanders reckon the effect will not be real “transparency”, but rather a “narrowing of the US stealth margin”. Despite China’s progress, says Admiral Cavanaugh, “our sensors are better than their stealth; and our stealth is better than their sensors. I know what submarine force I’d want my kids to be a part of.” American submariners,

moreover, know the Pacific better than anyone: “We’re walking the battlefield where we might have to fight.” But even America’s submarines face constraints. For one thing, they carry limited munitions. When they run out, they must sail thousands of miles to replenish them. In the course of a month, an aircraft-carrier can deliver hundreds of times more munitions than an attack submarine, a military source notes. What is more, there is a dearth of harbours suitable for submarines in the Pacific beyond the first island chain: mainly Guam, Pearl Harbour and now Perth. Belatedly, the navy is thinking of upgrading other ports. Specialised vessels can resupply submarines, but only in sheltered waters, and America has only two such ships in the Pacific. America and its allies may be able to mitigate the problem with cheaper and more expendable drones. Ukraine has shown prowess in using naval drones against Russian warships in the Black Sea. But these sail on the surface, under the control of Ukrainian operators. Communicating with uncrewed underwater vehicles (UUVs) is as hard as with submarines, which makes it difficult to keep a “man in the loop”. That raises ethical questions, though perhaps not unanswerable ones. A torpedo is a UUV of sorts, after all. Anduril, one of the emerging breed of “neo-prime” military contractors, has sold a version of its Dive-XL UUV called Ghost Shark to the Australian navy and is making prototypes for the American navy, too. Small enough to fit in a shipping container or cargo plane, its fibreglass body floods with water, with only small pressure vessels housing the most important components. Radio and acoustic gear allows communication; modular bays carry torpedoes, mines, sensors and more. China, too, is deploying a variety of uncrewed vehicles. Its “dolphin” wave-gliders use changes in buoyancy to propel themselves slowly, surveying the waters. Some Chinese military analysts have discussed using robotic “shoals” to confuse the enemy. In his office in Pearl Harbour, its walls covered with mementoes from the second world war and gifts from fellow submariners in allied navies, Admiral Cavanaugh sees advantages in “manned-unmanned teaming”. Drones can go deeper and be sent to riskier places than crewed submarines. “There’s certainly room for both,” he says. “But I don’t see the end of the crewed submarine any time in my lifetime.” ■

This article was downloaded by zlibrary from https://www.economist.com//international/2026/05/07/american-subs-rule-beneath-the- waves-but-chinas-are-catching-up