THE Chinese navy's recent foray into the waters between Indonesia and Australia is one more milestone in Beijing's increasingly bold maritime posture in the Indo-Pacific.
The three-ship exercise was also a wake-up call to anyone still doubting China's long-term intention to be able to project force in the Indian Ocean.
This demands new kinds of maritime security dialogue and practical surveillance co-operation among the region's maritime democracies, including Australia, Indonesia and India.
There was no warning of the exercise, but no lack of transparency in the subsequent Chinese official media reports. These referred to China's first combat simulation drills in the Indian Ocean as well as less warlike activities.
The amphibious warship Changbaishan, a so-called landing platform dock displacing 20,000 tonnes, is one of Beijing's more modern and sophisticated ships, and can deploy hundreds of marines. Together with the two destroyers accompanying it, Wuhan and Haikou, the squadron was an unambiguous demonstration of China's emerging ability to project force.
Since the end of 2008, China's navy has been one of many conducting anti-piracy operations in the Gulf of Aden. Although this activity has been seen as a testimony to the new Chinese commitment to safeguarding the global commons, it also has underlined the PLA navy's new capacity to carry out what it calls "far sea operations".
Some observers have claimed that the focus on territorial claims in the South and East China seas would downgrade the importance of the Indian Ocean in Beijing's strategic calculus.
Now, facts in the water have challenged those assumptions. China is going Indo-Pacific.
After crossing the South China Sea from its base on Hainan Island, the squadron transited south through the Sunda Strait, separating Indonesia's Sumatra and Java islands.
Somewhere between there and Australia's Christmas Island territory, it apparently conducted the combat simulation before turning east and sailing the length of Java.
It went back up north through the Lombok Straits between the Indonesian islands of Bali and Lombok, then the Makassar Straits between Borneo and Sulawesi and into the western Pacific.
This made use of the right of "innocent passage", although there is no suggestion the Indonesians were forewarned.
The path followed by the Chinese ships underlines the obsolescence of the notion that the Indian Ocean, South China Sea and East China Sea are neatly quarantined theatres of military activity.
The risk of confrontation in each of these zones matters to all the nations of Indo-Pacific Asia.
China has huge stakes in the Indian Ocean, the highway for most of its imported oil.
In the long run, securing the sea lines of communication in the Indian Ocean will likely be as much a strategic priority for China as the assertion of its maritime claims in the western Pacific.
In sending ships through the Indonesian straits, Beijing is telling Jakarta, Canberra and ultimately New Delhi that they should be prepared to see more of the Chinese navy in their proximity.
No sensible strategist would reject China's right to deploy capabilities to protect its interests, providing this is done in consultation with local powers and does not damage their interests or the stability of the regional order.
So the challenge is not about keeping China out of the Indian Ocean. It is about integrating China as a partner in a rules-based system, and one that equally accepts India's growing maritime links with the Pacific.
What the region cannot afford is for the expanding economic and strategic interests of great powers to translate into destabilising activities that occur unilaterally and without warning.
Indonesia is conscious of this challenge, given its Foreign Minister Marty Natalegawa's initiative of an Indo-Pacific treaty for peace and co-operation, as well as his efforts to build Southeast Asian solidarity on a code of conduct in the South China Sea.
Australia does not seek a confrontation with China, its largest trading partner. But given Australia's dependence on maritime trade and regional stability, and the security importance of the continent's northern approaches, the Chinese exercise is likely to influence Australia's defence debate as the drafting of a new white paper gets under way.
There will be a renewed focus on the need for the best possible maritime domain awareness, in partnership with the US but perhaps third parties, too.
At a time when Australia-Indonesia relations are strained over short-term differences, it is important not to lose sight of the longer-term strategic logic of these two countries learning to share information about all maritime activity in the waters between them.
The idea of a three-way security dialogue between Australia, India and Indonesia has evolved quietly across the past five years.
Its logic is now becoming compelling. And this should go further, to lead to practical maritime and naval co-operation.
While Australia-Indonesia ties are in limbo, it would make sense to deepen the Australia-India side of the triangle. Here the potential areas for action are maritime domain awareness, naval intelligence sharing, providing access to each other's naval facilities, and working together to improve the capacity of smaller states in the Indian Ocean.
China has the right to advance its interests in the Indian Ocean just as the Indian Ocean's resident powers have every right to work together to monitor and manage the changes ahead.