In June, US Navy Chief of Naval Operations (CNO) Admiral John Richardson said during a speech at the US Naval War College that the US Navy should terminate its current practice of dedicating several US Navy warships solely for Ballistic Missile Defense (BMD).

Richardson wanted US warships to halt BMD patrols off Japan and Europe as they are limiting, restrictive missions that could be better accomplished by existing land-based BMD systems such as Patriot anti-missile batteries, the US Terminal High Altitude Area Defense (THAAD) anti-missile system and the Aegis Ashore anti-missile system.

In the months since dropping his bombshell, Richardson – and much of the debate – has gone quiet.

“My guess is the CNO got snapped back by the Pentagon for exceeding where the debate actually stood,” one expert on US naval affairs told Asia Times.

But others agree with him. Air Force Lt Gen Samuel A Greaves, the director of the US Missile Defense Agency (MDA), acknowledges Richardson’s attempts to highlight how these BMD patrols were placing unwelcome “strain on the (US Navy’s) crews and equipment.”

But there are complications. While it may free US Navy warships for sea-control, rather than land defense, there is a concern that next- generation hypersonic cruise missiles could defeat land-based BMD systems, such as Aegis Ashore, while the US Navy’s Aegis-equipped warships offer the advantages of high-speed mobility and stealth, resulting in greater survivability overall.

As Japan prepares to acquire its first Aegis Ashore BMD system – and perhaps other systems such as the THAAD system which has been deployed previously in Romania and South Korea – the possibility that the US Navy will end its important BMD role represents abrupt change.

Could it happen?

Professor James Holmes, JC Wylie Chair of Maritime Strategy at the US Naval War College, hopes the US Navy “offloads that mission, at least as a vessel’s chief mission at sea.”

“One imagines we will, especially since the money for a 355-ship navy may not be forthcoming. We will have to squeeze more combat power out of existing assets,” Holmes told Asia Times. “So when you divert an Aegis combatant to missile defense you are not devoting it to a destroyer’s chief purposes, namely fighting enemy maritime forces for command of the sea and then making use of the sea to project power afterward.”

Garren Mulloy, Associate Professor of International Relations at Daito Bunka University in Saitama, Japan agrees that there is a good prospect it will happen, but for a very different reason.

“The White House sees little need for US missile defense efforts, given that US President Donald Trump believes the bulk of the problem has been solved,” said Mulloy. “The USN ships were there primarily not for Japanese, but for US mainland forward defense – to intercept or deter [North Korean] ballistic missiles overflying Japan. And that is how the US tended to view the [Japanese Maritime Self Defense Forces’] effort as well.”

Meanwhile, Trump’s threats to cut US defenses in Japan have not been borne out, Mulloy observed.

Japan swallows the cost

While Japan has to face the cost of installing Aegis Ashore, two Aegis BMD-capable warships, each worth US$2 billion, are required to fulfill a single BMD mission at sea, whereas “a single land site could presumably accomplish the same goals,” Holmes said.

Hence, Aegis Ashore makes more sense.

Mulloy sees Japan’s options as unchanged from a year ago. Its Aegis destroyers are operational and Aegis Ashore will just expand on Japan’s offensive missile deterrence capabilities. “These two issues were really introduced into the defense budget at the same time almost exactly a year ago,” said Mulloy.

Japan’s decision to deploy Aegis Ashore can fill in any gap created by a possible US Navy cessation of BMD patrols. “The land-based option is more reliable, less logistically draining, and despite being horrendously expensive, could be effective in the sense that it provides a degree of reassurance to the Japanese people and US government, and introduces an element of doubt of missile efficacy into [North Korean] calculations,” said Mulloy, adding, however, that these systems could not cover Okinawa.

“Fixed sites in Japan could be vulnerable, and the Aegis vessels provide
a flexible forward-defense, before anything enters Japanese airspace,
but with obviously limited reactions times,” Mulloy said. “Aegis Ashore gives more reaction time – but over Japanese airspace.”

How will China and Russia respond?

Unlike the furious reaction from China to South Korea’s deployment of a US THAAD battery on its soil, Holmes is not anticipating the same from China – or Russia – in this instance.

“If the US Navy offloads the BMD mission and Japan picks it up, whether through Aegis ships at sea or Aegis Ashore, the net change in our defense posture as an alliance – and thus in the military balance – will be minimal,” said Holmes. “Beijing could beat Tokyo around the head for militarism, etc, but that is standard fare.

“Modifying Japan’s helicopter-equipped destroyers for the F-35B would probably trigger a much louder response out of China,” Holmes added. “That is a serious departure for post-war Japan.”

But Mulloy expects Russia and China to become more worried, given that any expanded Japanese BMD defense could provide greater asymmetry for US nuclear forces.

“[US nuclear forces] are protected from ballistic missiles by the Japanese system while the Chinese and Russians are potentially open to attack,” said Mulloy. “Given China’s concern that a Japanese cruise missile force could pose threats to the Peoples Liberation Army’s Navy in the East China Sea or even the South China Sea, this might have a multiplying effect.”

The silence is deafening

Yet, amid ongoing radio silence about the US Navy’s BMD mission, experts do not see any attempt underway by Japan to create a new BMD system or warship. However, Japan continues to develop new and improved sensor technologies that can vastly improve the overall performance of BMD interceptors.

“While the Acquisition, Technology and Logistics Agency is developing technologies such as sensors that can be used for BMD, it is not developing BMD systems which can replace US-led systems,” said Professor Narushige Michishita, director of the Maritime Safety and Security Policy Program at the National Graduate Institute for Policy Studies in Tokyo.

The silence about this sudden possible shift in the US defense posture in the western Pacific is understandable: it is a sensitive topic in Washington and Tokyo. However, the Trump administration has urged its allies to pay more for their own defense needs and to support US troops deployed overseas.

Meanwhile, Tokyo needs to proceed cautiously given the likelihood that neighbors might view a move on BMD as evidence that Tokyo is adopting an increasingly aggressive defense posture in the region.

But for them, it is a no-win situation. If the US does ditch the BMD patrol mission, China and North Korea might view the shift as equally menacing given that it greatly enhances the US Navy’s maritime warfare capabilities.