For all the heated talk of the US military's strategic 'pivot' to the region, the scene in Guam's Apra Harbour over recent days is a reminder that the shift has been well under way for some time.
Six US submarines surfaced in Guam - the closest piece of US territory to the Chinese coast - for resupply and repair in the biggest public display of the US Navy's forward-deployed submarine presence in a decade, according to a little-noticed naval announcement.
The vessels represent the leading edge of a repositioning of US submarines from the Atlantic to the Pacific in recent years along a 60:40 split - precisely the formula for the broader US fleet announced by Defence Secretary Leon Panetta two weeks ago in Singapore.
Completing a policy hatched during the administration of president George W. Bush, some 31 of the US Navy's 53 fast attack submarines are now based in the Pacific - including three in Guam, due east of the Philippine capital, Manila.
Though far less visible than other naval assets, submarine deployments are among the most closely scrutinised given the highly sensitive nature of their work. While they are equipped with weapons such as torpedoes and guided missiles, it is their other, more discreet capabilities that attract interest - an expanding range of intelligence-gathering devices, and the ability to track rival submarines and surface ships and to release special-forces teams secretly.
'The Pentagon's forward deployment of its submarines is the harder edge of its presence in the region,' a veteran Asian military attache said. 'None of this is lost on regional militaries, and China is paying particularly close attention.
'You always have to remember that submarines routinely do things that would be either highly provocative or impossible for a surface ship to attempt in peacetime, like penetrate a coastline or closely shadow a foreign vessel or submarine. And when it comes to other nations' territorial waters, it has always been a case of 'just don't get caught'.'
