The Navy could procure roughly seven diesel boats for the price of one nuclear-powered boat—and boost the inventory toward 66 subs far sooner than midcentury.

We need to break the orthodox approach to naval fleet design. The US Navy urgently needs to expand its fleet of attack submarines, and time is short. The navy leadership’s goal is a fleet of 66 nuclear-powered attack submarines (SSNs). The silent service currently stands at under 50 SSNs—and stagnating—while we and our allies enter the period of maximum danger in the Western Pacific. The submarine industrial base needs to double production in order to reach the desired inventory of attack boats. That will not happen in time for a potential conflict with China in the “Davidson Window,” circa 2027.

One way to add firepower at low cost relative to SSNs would be to purchase diesel-electric attack submarines (SSKs) from a foreign manufacturer that has a hot production line and could set about mass-producing them. For instance, the Japan Maritime Self-Defense Force operates a contingent of SSKs acclaimed as the finest large conventionally powered subs on the planet. The first Japanese Taigei-class SSK, built by Mitsubishi Heavy Industries, cost Japanese taxpayers about $690 million. Subsequent units evidently cost substantially less. But so as not to stand accused of gaming the numbers, let’s use $690 million as the per-boat figure for the sake of discussion.

Meanwhile, the latest “Block V” Virginia-class SSNs will set American taxpayers back some $4.8 billion per unit—and cannot be built in a hurry, as our yards’ performance shows. That means the Navy could procure roughly seven diesel boats for the price of one nuclear-powered boat—and boost the inventory toward 66 subs far sooner than midcentury, the timeframe designated in the Navy’s latest 30-year shipbuilding plan (fiscal year 2054 to be exact).

To be clear, I am not necessarily advocating canceling one or more Virginias to free up funding for SSKs. In a perfect world, I would like to have it all. The naval-nuclear-propulsion mafia tends to hyperventilate when someone proposes reviving diesel propulsion in the fleet. They see SSKs as a threat to the prized SSN force, fretting that green-eyeshade types might substitute cheaper platforms for better ones to save money. I’m just quoting the Virginia price tag to show how the Pentagon and the Navy could augment the submarine tally with good-enough platforms quickly, and for a modest additional sum.

More hulls for a fraction of the cost, and delivered in a timely manner, sounds efficient in terms of tactical adequacy, engineering risk, production cadence, and price tag. But to what end? Well, the navy could buy a squadron of SSKs and permanently forward-deploy it to the Western Pacific to help shore up allied defenses along the first island chain, consonant with operating concepts such as distributed maritime operations and expeditionary advanced base operations. Operating subs in this manner is nothing new. Japan’s navy has used SSKs to monitor and obstruct communist access to the Western Pacific since the 1950s. A squadron of American diesel attack boats would augment allied prowess beneath the waves in the theater of prime importance to the Defense Department—and do so efficiently.

Nor should the Pentagon confine this inventive approach to undersea warfare. There are similar ideas out there for surface warfare. For instance, one Coast Guard officer advocates fitting out a flotilla of 350-ton fast-response cutters (FRCs) at $65 million per unit—arming them with antiship missiles, painting them haze gray, and dubbing them missile patrol craft. That production line is hot as well, and it’s based at a Gulf Coast shipyard rather than overseas. The author projects that the Navy could take delivery of twenty missile cutters within five years, for the price of a single Constellation-class frigate—a troubled program that is well behind schedule, over budget, and faces an uncertain future. Upgunned cutters plying the Western Pacific could make a substantial difference in strategic competition and warfare.

Like a turn to diesel submarines, such a move would be an obvious and efficient choice for fleet designers. We need numbers, and fast. Let’s break the mold—and think in novel ways.