On July 14, Indonesia took a major step forward in confronting China’s South China Sea claims with an announcement that it was renaming a part of the sea in its territory the “North Natuna Sea,” becoming in a single act the most important Southeast Asian nation to stand up to Beijing.

That may have come to many as surprise – certainly to the Chinese, who called on Indonesia to stop using the term on official maps and documents with a diplomatic note, written in Mandarin, from the Chinese Ministry of Foreign Affairs to the Indonesian embassy in Beijing.

Nonetheless, the Indonesians are sticking to their guns. The new name encompasses an area north of the Natuna islands that partly falls within China’s “nine dash line,” by which Beijing claims the sea stretching 1500 miles from its mainland coast almost to the shores of Malaysia, the Philippines, Brunei, Vietnam, and Indonesia.

The naming was a reminder of how seriously Indonesia treats its position as the seat of ancient trading empires and the location of some of the world’s strategically most important straits – Melaka, Sunda, Lombok and Makassar. Since he was elected in 2014 President Joko Widodo has made maritime issues central to Indonesia’s foreign policy, building up its navy, arresting and dynamiting dozens of foreign ships caught fishing illegally, and taking a quiet but firm stand on sea rights.

In December of 1957, Indonesia declared that it was an archipelagic state, at the time a revolutionary move and a direct assault on the assumption by the major western powers that territorial seas extended only three nautical miles from actual coastlines, and that the seas otherwise were open to all.

The 1957 Indonesian claim helped set in motion 25s years of negotiations that led eventually to the United Nations Convention on the Law of the Sea, signed in 1982 and which finally came into force in 1994, along with an implementation agreement which opened the way to ratification by western powers which had had some reservations. Most developing countries, including China, had already signed up. (The US has accepted its provisions in practice but has still not ratified it). The Convention formerly enshrined the archipelagic principle, which by then had become widely accepted in practice.

In total there were 37 years of negotiations on the whole range of complicated issues relating to territorial seas, internal waters, rights of innocent passage, particularly through important straits, rights to fish and seabed resources, continental shelf issues, air transit rights etc. Indonesia continuously played a leading role.

That was natural given that it is, by far, the world’s largest archipelagic state and owns all or part of several of international commerce’s most important straits – Melaka, Singapore, Sunda, Karimata, Lombok and Makassar. But success required the continuous and detailed engagement of the nation’s foremost diplomats, notably Mochtar Kusumaatmadja and Hasjim Djalal who remained on the case through all the political turmoil of 1960s’ Indonesia and through to the 1970 and 80s when Mochtar was foreign minister.

The broad story has been told before, including by Hasjim Djalal’s son, Dino Patti Djalal, formerly Indonesia’s ambassador in Washington, but John G Butcher and R E Elson, two Australian academics, have written the most detailed account of the negotiations and Indonesia’s role in them in their book “Sovereignty and the Sea: How Indonesia Became an Archipelagic State,” published by NUS Press in Singapore. It is an impressive work of scholarship which could have been even better had the authors been given access to Indonesia’s own National Archives or those of its Foreign Ministry. Thus they had to rely on British, US, Dutch and Australian records dealing with various aspects of the negotiations, and those of Fiji, another archipelagic state which played an active part,.

The book also used secondary works and interviews with key participants, including Hasjim, Mochtar and Tommy Koh, Singapore’s lawyer/diplomat who as President of the 1980-82 UN Conference played a key role in bringing the negotiations to their conclusion with the 1982 Convention.

In addition to dealing with big power interests, demanding sea and air access rights and strict limits on the resources claims of littoral states, the Indonesians had a hard time trying to keep neighbors on their side. The Philippines was helpful enough as a large archipelago in its own right and possessor of the internal Sulu Sea. But Malaysia was a major headache given that its interests in communication between its mainland and Borneo territories as well as their offshore and fishing resources ran up against Indonesia’s baseline claims.

Eventually formulae were devised which Malaysia could accept and were applicable in similar situations elsewhere. Japan, though an archipelago itself, was also a problem due to its huge fishery interests. But even before finally coming into force, the 1982 UNCLOS provided a basis for bilateral agreements on boundary, fishing and seabed issues. And the region has, unlike China, lived up to promises to accept international judgments – such as on boundary disputes between Singapore and Malaysian and Indonesia and Malaysia.

Butcher and Elson authors show how delicate sea questions could be. During Indonesia’s konfrontasi or undeclared war with Malaysia in 1964, Britain wanted to send a warship to Australia using the Sunda Strait over which Indonesia claimed ownership but which the British insisted was an international waterway. After some quiet diplomacy, the British opted to go the longer way via the equally Indonesian but less sensitive Lombok strait in return for an assurance that Sunda would remain open. London ordered its navy always to give advance notice of passage to Indonesia. These were the kind of steps which over time were to make a realty of most – but not all – of Indonesia’s 1957 claims. Likewise was a temporary informal deal with in 1968 provided Japanese fisheries organisations access to the Banda Sea and its tuna stocks.

Given maritime Asia’s key role in UNCLOS, the book by the two Australian authors is an important if silent reminder of the demeaning nature of President Duterte’s undermining of his own country’s victory at the Permanent Court of Arbitration on UNCLOS issues in return for promises of cash from China. It is also an insult to those from the region who made the Convention and formal acceptance of the archipelagic principle possible, particularly Indonesians but including Philippine diplomats and Singapore’s Koh. The 1982 Convention is a document of critical importance to the maritime states of the region. They forget it at their peril.