If it’s good for China to procure diesels for anti-access/area-denial purposes in the near seas, then it’s good for Americans and Japanese if they want to deny the denier access it covets.

What madman would propose adding diesel submarines to the U.S. Navy’s all-nuclear silent service?

There are a few. The topic came up at an early March hearing before the U.S. House Seapower and Force Projection Subcommittee. Representatives from three teams that have compiled competing “Future Fleet Architecture” studies convened to debate their visions with the committee. Published by the Navy Staff itself, the Center for Strategic and Budgetary Assessments, and the MITRE Corporation, the studies explore everything from overall ship numbers to the types of hulls comprising the future fleet to the mix between manned and unmanned platforms.

Navy potentates will now evaluate and compare the studies. The end product will be an official navy statement about force-structure questions, useful to Congress as lawmakers determine how many—and which—ships, planes, and armaments to fund. One consensus, however, already unites the protagonists to this debate: the U.S. Navy needs more of just about everything. The navy estimates it needs 355 vessels to fulfill its missions in increasingly contested settings, principally around the margins of Eurasia. That portends about a 30 percent boost to the force.

(This first appeared in March 2017.)

A naval expansion of such proportions will put a premium on low-cost yet effective platforms that can be acquired in bulk. Diesel-electric submarines constitute one such platform. The last boat in the Japan Maritime Self-Defense Force’s (JMSDF) Soryu class—a class widely acclaimed the world’s finest of its kind—ran Japanese taxpayers $540 million. Let’s use that as a benchmark for discussion. Meanwhile, each Virginia-class nuclear-powered attack boat sets back American taxpayers a cool $2.688 billion. That’s five for the price of one—a low, low price by any standard!

Reports Megan Eckstein of USNI News, however, Charles Werchado, the deputy director of the Office of the Chief of Naval Operations’ assessments division, “firmly denounced” the MITRE analysts’ vision of a hybrid nuclear/conventional submarine force. Quoth Werchado:

“If I was a country like China, I would buy a lot of diesels because I know you’re going to come and fight me here at home. We have to deploy, and the only way to deploy is to bring your own fuel with you. When we buy a Virginia, it comes with a lifetime of fuel. So I have nothing against diesel submarines, but you have to say, am I’m going to be fighting within 200 miles of where I’m based at? Or else now I have to buy extra oilers. I’m going to make them vulnerable when I refuel them; they’re going to have to snorkel and they’ll become vulnerable. It’s just not an option for us as long as we have to be a global navy."

He thus objected to diesels based on geography, logistics, and military capability. Let’s take those objections in turn. First, geography. Werchado’s critique seemingly presupposes that a U.S. diesel contingent would be based on U.S. territory—in other words, no closer to East Asia than Guam. QED: diesels are a non-starter. They would be positioned too far from the Yellow and East China seas, a likely combat theater, to do much good. And indeed, the cruising-range limitations on diesel boats are real and immutable. But let’s not overstate their impact. Distance can be managed through savvy force dispositions on the map.

In fact, if it does things wisely, the U.S. Navy can turn technical shortcomings to strategic and political advantage. Here’s how: it could procure a squadron of diesel boats in large numbers, station it permanently in the Far East, close to potential scenes of action, and place it under a combined U.S.-Japanese submarine command. Doing so would confer a host of benefits. Forward basing would obviate the range problem. For instance, Soryu-class boats boast a cruising range of 6,100 nautical miles—more than adequate for prowling the depths in Northeast Asia. A U.S.-Japanese force founded on a common hull—whether the Soryu or some other design—could presumably match or exceed this performance.

Nor would this represent some leap in the dark. Diesel subs have proven themselves in Northeast Asia across many decades—witness the U.S. submarine campaign against Japan during World War II. And after six-plus decades of practice dating to the JMSDF’s founding, Japanese subs excel at regulating east-west movement through the first island chain, as well as north-south movement along the East Asian periphery. Indeed, undersea warfare represented one of Japan’s chief contributions to allied strategy during the Cold War. Japanese boats lurked along the island chains to detect and trail Soviet subs trying to exit the Seas of Japan and Okhotsk for the broad Pacific Ocean. Soviet skippers commonly sheltered within Asia’s near seas rather than make the attempt.

This constitutes an ideal approach for an age when island-chain defense is regaining its prominence in allied maritime strategy. Want to deter China from seizing the Senkaku Islands or venturing other forms of aggression? Threaten something Beijing prizes dearly, namely ready access to the Western Pacific. Proliferate subs in Northeast Asia, and demonstrate the capability to use them to bar the straits piercing the first island chain. That should give Beijing pause when the leadership contemplates adventurism. If it’s good for China to procure diesels for anti-access/area-denial purposes in the near seas, then it’s good for Americans and Japanese if they want to deny the denier access it covets.

So the strategic logic cuts both ways. Now think about such a deployment from an alliance-relations standpoint. China is a breaker of alliances. It hopes to divide the allies into manageable bits while dislodging the United States from its strategic position in the Western Pacific. Accordingly, Tokyo fears abandonment by its superpower patron. How better to make a statement about American steadfastness than by permanently forward-deploying a fleet of submarines to Japan while embedding U.S. boats and crews within a multinational command? That would show America is in Asia to stay.

And heck, if Tokyo and Washington were willing to take the diplomatic heat from Beijing, they could even equip the Taiwan Navy with a flotilla of diesel boats built on the common design. The George W. Bush administration offered Taipei eight diesel submarines sixteen years ago. But no American shipbuilder has constructed conventional subs in decades, while no foreign government was prepared to help construct the craft—and thereby incur Beijing’s wrath. The deal languished.

Now might be the time to consummate it. Supplying the boats would help Taiwan defend itself, replacing its flotilla of two Dutch-built subs of 1980s vintage and—astonishingly—two World War II-era relics. And furnishing Taipei with boats interoperable with the U.S.-Japanese diesel fleet would allow for coordinated operations should the allies summon the political moxie to work with Taiwan. A diesel program, then, could open new strategic and diplomatic vistas.

Second, logistics. The U.S. Navy combat-logistics fleet doubtless needs expanding, but not because of prospective conventional subs. Forward-deployed U.S. boats would presumably adopt Japanese logistical patterns, meaning they would go on patrol and refuel in port after returning from sea. Now, the allies could stand to bolster their shore logistical arrangements. China’s military would not exempt Japanese seaports such as Yokosuka and Sasebo from attack in wartime. If it did so it would grant its foes a safe haven for naval warmaking. Missile strikes would be sure to come, and might impair or disable shore infrastructure—starving the fleet of precious fuel and stores.

To cope with this prospect, the allies should rediscover their Pacific War past. During its westward advance across the Pacific, the U.S. Navy fashioned techniques and hardware to refuel, resupply, and repair ships from dispersed, often improvised island bases. The allies should ransack history for insight—thinking ahead about how to use Japan’s many islands and inlets as impromptu logistics hubs. But again, the allies need to make themselves resilient as a matter of course. After all, the conventionally powered surface fleets based in Japan need fuel too. And nuclear-powered warships need every other form of replenishment except fuel for their main engines. (Try running aircraft-carrier flight operations without jet fuel.) Logistical demands, in short, are hardly unique to diesel subs.

And third, diesel subs’ supposed vulnerability. Diesel subs have to surface periodically to snorkel, taking in air to help power their engines. They’re exposed to radar detection while snorkeling. Soryu-class boats, however, sport “air-independent propulsion” that lets them stay submerged for up to two weeks. JMSDF commanders and their political masters evidently find the design wholly adequate, while Japanese submariners have mastered tactics and deployment patterns that let them reach Northeast Asian patrol grounds, loiter on station for a satisfactory amount of time, and return to port.

Adding American boats would impart mass to the fleet—further easing the challenge of keeping enough boats plying the deep. The more subs in the rotation, the shorter voyages can be. Bottom line, having the fleet make its home near likely Asian hotspots would solve many ills, as would expanding and diversifying logistics arrangements. Such measures, furthermore, would cow prospective antagonists while comforting allies and friends. This constitutes a promising venture in manifold respects.