Submarines and nuclear umbrellas
4 Jan 2023|

Late in 2022—a year of war, pandemic, climatic disaster and attempted nuclear coercion—a number of news outlets published a photograph of a rare event. True, the photograph was of particular interest to only a small range of viewers: those with an unwholesome fixation on strategic nuclear arsenals. It showed a US Ohio-class ballistic missile submarine (SSBN), USS Tennessee, on the surface alongside a British Vanguard-class SSBN, somewhere in the Atlantic. Ballistic missile submarines (colloquially called ‘boomers’) from different nations surfacing alongside each other is extremely unusual. But the photo, taken on 22 November during joint training, also included a helicopter apparently conducting anti-submarine warfare (ASW) and a low-flying E-6B Mercury aircraft.

It’s a picture loaded with firepower. The American SSBN has 20 launch tubes, and while the individual warhead loading on each Trident missile may vary, the submarine is probably carrying around 90 warheads. The British SSBN is probably carrying another 40. And then there’s the aircraft. The E-6B has two missions: to act as a relay channel of communications to the US SSBNs, and to support US Strategic Command’s National Command Authority. In its latter mission, the aircraft embarks a small battle staff capable of launching intercontinental ballistic missiles.

The photo was publicly released on 13 December. There’s a lot going on in it, so let’s disentangle the messages. I see five: of alliance solidarity, SSBN survivability, ASW superiority and a resilient line of command authority to deter any attempted decapitation strike against Washington or London. Moreover, it is a reminder to Russian President Vladimir Putin—and the world more generally—what classical nuclear deterrence looks like.

What’s interesting is that the SSBN leg of the triad has been selected to convey those messages. In recent history, ballistic missile submarines have been—for Western nuclear powers at least—the last guardrail of nuclear deterrence. Cruising silently and invisibly in the ocean’s depths, virtually invulnerable to surprise attack, they’re the heart of the US’s assured second-strike capability.

But in this case, the boomers have moved from the invisible realm to the visible. Moreover, US SSBNs have been behaving unusually elsewhere too. USS Rhode Island made a port call in Gibraltar on 1 November. That came hard on the heels of the West Virginia’s port call at Diego Garcia from 26 to 31 October. Since the West Virginia operates out of King’s Bay in Georgia, making a port call in Diego Garcia shows the impressive reach of the boomer fleet. The same submarine had, a couple of weeks earlier, surfaced in the Arabian Sea (of all places) to embark the commander of US Central Command—an implicit message to those who think of US nuclear commitments solely in relation to Europe and the Indo-Pacific that CENTCOM is also linked to the US nuclear deterrent.

What makes the recent wave of port calls a little more puzzling is that US boomers have been going out of their way to prove that they are not dependent on pier-side operations. Granted, during the visit to Diego Garcia, the West Virginia conducted a crew change. But in May 2022, the Alabama demonstrated the ability to swap Blue and Gold crews at sea. And a couple of months later, two SSBNs exercised ‘vertical replenishment’—a fancy name for aerial resupply—while at sea. Washington seems to be signalling that, in a crisis, it is not dependent on port visits to stay on station.

Such visits by US SSBNs have been comparatively rare in recent decades, although in earlier history they used to be more common. The first such visit occurred in April 1963 when USS Sam Houston visited Izmir in Turkey, part of Washington’s attempt to assure the Turks they were still covered by the US nuclear umbrella after the removal of the Jupiter missiles as a tacit coda to the resolution of the Cuban missile crisis.

As the big ballistic-missile-carrying submarines became increasingly defined as the most survivable leg of the US nuclear triad, as the ranges of submarine-launched ballistic missiles improved, and as the possibility of some form of terrorist attack on a submarine in a foreign port went up after the attack on USS Cole, and up again after the 11 September 2001 terror attacks, American SSBNs stayed at sea, on patrol. In 2003, the boats were specifically instructed not to conduct port visits, except to US naval facilities. That rule lasted for 12 years, until late 2015. But even after that, port visits remained unusual. Security is still an important consideration. During the visit to Gibraltar, USS Rhode Island was virtually bubble-wrapped.

Of course, there’s a second part to this story. To fully appreciate what’s happening, readers need to remember the events of 1991. The Cold War was over. And on 27 September, President George H.W. Bush outlined several presidential nuclear initiatives designed to reduce the number of forward-deployed nuclear weapons and to relocate those weapons back to the continental United States. The initiatives covered ship-borne warheads as well as land-based ones, and the effect was to ‘denuclearise’ a large percentage of the US Navy. All surface ships and most submarines—SSBNs were the exception—no longer carried nuclear weapons.

But the world of 1991 didn’t last. In particular, the rise of Asia and the return of great-power strategic competition began to bite. Allies and partners, looking for clearer signals of a US nuclear commitment to their defence, became less enamoured of the non-nuclear navy. That was especially true in the Indo-Pacific, largely a maritime theatre. If the US Navy wasn’t going to contribute to extended nuclear assurance in the region, who was? The air force could certainly deploy highly visible strategic bombers to the region during crises, but the effect was somewhat monopedal.

The recent US nuclear posture review shows that Washington is beginning to think more deeply about the future shape of US extended nuclear deterrence. In the Indo-Pacific, extended deterrence arrangements have traditionally played second fiddle to those in Europe. But the review foreshadows denser consultations, higher-level engagements and, where agreeable, boomer port visits and strategic bomber missions. Such visits would be intended to assure allies and partners of Washington’s continuing commitment to ‘extend’ its strategic nuclear deterrent to the protection of their vital interests.

South Korea looms as a possible starting point, not least because it hosted a steady procession of US SSBNs in earlier decades. Japan and Australia are likely seen as more sensitive cases: neither is accustomed to seeing a visiting SSBN as a form of assurance.

Still, nuclear deterrence is already playing an increasingly large role in the Indo-Pacific, and that role is more likely to grow than shrink. Australian policymakers should be alert to the fact that the nuclear umbrella in the region is taking on a new and more visible form. And we have a special interest in the shelf life of US extended deterrence—putting it brutally, we’re not as well placed as some other US allies to pursue what might euphemistically be called ‘alternative options’.