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.