With no national laws applying there are many things that can be done in international waters such as fishing, travelling, scientific experimentation, laying of pipes and cables and, it turns out, conducting naval live-firing exercises.
Most New Zealanders had barely given a moment’s thought to the People’s Liberation Army Navy until Friday, when Chinese vessels the frigate Hengyang, the cruiser Zunyi and supply vessel Weishanhu set all guns blazing well off the coast of Tasmania.
Whatever the vessels were firing at, they landed a square hit on New Zealand public opinion and public perception of China.
While the ships are closer to Australia than New Zealand they have also had a practical effect on this country: transtasman flights having had to make sudden detours to avoid the risk of being caught in any actual crossfire.
However, there has been plenty of the metaphorical kind in subsequent days as New Zealand and Australia have sent diplomatic please explain notes to China asking just why these three ships have popped up in our vicinity.
They will have had to be very delicately written: China is the largest trading partner of both New Zealand and Australia and neither country can afford to upset a great power.
Hence, both New Zealand and Australia’s prime ministers have repeatedly stressed that China has not breached international law, but there are certainly questions to be answered by China, a country not normally disposed to explaining itself in public.
All armed forces have to carry out live-firing trials to ensure that combat systems work as intended, in particular things like missile interception systems where a considerable amount of vacant space is required in case things do not go according to plan.
Finding somewhere for such testing is difficult, particularly for a navy like that of China. It has some of the busiest territorial waterways on the planet, and the nearest international waters lie south of the Philippines.
Naval vessels from other countries sailing international waters near New Zealand is not unprecedented but it is rare, and live-fire exercises even more so. Such things are difficult to document as they are far from land and seldom publicised, but experts and officials have struggled to recall any similar such incident.
Diplomatic courtesy would normally require a heads-up so as not to cause alarm — Australia, when it does similar exercises, gives New Zealand 12 to 24 hours’ notice. The lack of any such message suggests that causing alarm was exactly what China was intending by authorising this high seas cruise.
If Australia and New Zealand know precisely what message China has sent it they have not been forthcoming about it, but speculation suggests that it has something to do with each country having had naval vessels sail through the Straits of Taiwan in recent times.
Last September, the RNZN tanker Aotearoa sailed through those hotly contested waters in convoy with the Australian destroyer Sydney.
It was the first time a New Zealand naval vessel had been in that part of the world since 2017 and it was returning from United Nations operations off the coast of North Korea, a transit which had nothing to do with China.
Defence Minister Judith Collins doubted that that was why China had sent a flotilla to our part of the world, but she has advanced no other more plausible option.
Another theory has linked the decision to hold this exercise here and now to the Cook Islands signing a co-operation agreement with China last week. That would have taken considerable pre-planning to achieve, though, quite apart from being a highly excessive reaction to any New Zealand protests.
Another possibility is that China is firing a warning shot in relation to any possible expansion of the Aukus defence agreement.
For now, the cliche of keeping calm and carrying on seems to be the best option. That said, this incident is a stark reminder that the balance of power is changing in the Pacific, and that the world’s troubles are not so far away as we might suppose.
Cabinet will soon be considering the Defence Capability Review, a strategic document which, all of a sudden, has taken on far greater significance.
