On 25 April, the modified Ohio-class nuclear-powered cruise-missile submarine (SSGN) USS Michigan docked in the South Korean port of Busan. The US Navy called the visit ’routine’, but the timing of it, in a period of tension on the Korean Peninsula, and the prominence given to it were anything but.

USS Michigan. Credit: US NavyBy Nick Childs, Senior Fellow for Naval Forces and Maritime Security

The very overt way in which the submarine’s arrival in Busan was used for strategic messaging ran counter to the traditional covert nature of submarine operations. However, it was in line with the trend in the US Navy in particular, but also among other navies with power-projection ambitions, for submarines to take an increasing role in supplementing traditional power-projection ’big sticks’ like aircraft carriers and other major surface warships. The increasingly contested nature of the maritime domain is likely to see that trend strengthen with growing pressure for submarines to take on even more multi-mission power-projection capabilities in the future.

President Donald Trump himself obliquely telegraphed the USS Michigan’s arrival in Busan as part of his administration’s admittedly somewhat confused messaging on naval deployments heading towards the Korean Peninsula, including the despatch of the USS Carl Vinson carrier strike group. On 11 April, Trump told Fox Business News: ’We are sending an armada. Very powerful. We have submarines. Very powerful. Far more powerful than the aircraft carrier, that I can tell you.’ Whether it was intended to be or not, it was a very striking use of a submarine as a tool of latter-day ’gunboat diplomacy’.

Each of the US Navy’s four Ohio-class SSGNs (converted from their original ballistic-missile-carrying role) can carry 154 Tomahawk land-attack cruise missiles (TLAMs). They also have capacity to support 66 special-operations personnel, including covert deployment via dry-dock shelter; have significant sensor and communications suites; and are armed with torpedoes. They are seen in some ways as an incarnation of the ‘arsenal ship’ concept.

The first operational use of an Ohio-class SSGN came in the 2011 NATO-led Libya campaign. Then, the USS Florida launched more than 90 TLAMs. As a comparison to underscore the capability housed on one hull in the Ohios, the total US punitive strike launched against Syria in April 2017 amounted to 59 TLAMs fired from the destroyers USS Porter and USS Ross. (Also of interest is that the commander of the US submarine force at the time the USS Florida deployed to Libya was then Vice-Admiral John Richardson, now a full admiral and US Chief of Naval Operations. And the then-commander of the US 6th Fleet in Europe is now the head of Pacific Command, Admiral Harry Harris.)

The challenge for the US Navy is how to replace this capability, as the Ohio-class SSGNs are scheduled to leave service the middle of the next decade. The Block V and later versions of the Virginia-class attack boats, with 40 TLAMs each, are meant to be at least a partial answer. What the ultimate fate of the Ohios might be, given proposals to raise the target force for the US Navy from 308 warships and submarines to at least 350, may also be open to question.

The other fleet developing a significant SSGN force is the Russian Navy. It has the highly capable prototype Yasen class, the Severodvinsk, with further improved versions in build, and is in the process of modernising its Oscar II boats. For now, though, Moscow seems content to utilise its submarine force very much in a traditional covert manner, albeit still with significant strategic impact given the number of warnings about increased Russian submarine activity emanating from senior US and NATO naval commanders.


This analysis originally featured on the Military Balance+, the new IISS online database that enables users in government, the armed forces and the private sector, as well as academia and the media, to make faster and better-informed decisions. The Military Balance+ allows users to customise, view, compare and download data instantly, anywhere, anytime.

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