One of the more pressing geopolitical issues of our time has to do with the role of the United States as the world’s pre-eminent military power – or, as Americans like to think of it, its role as the global policeman and leader of the free world. And any consideration of that question leads inevitably, if not immediately, to a discussion of American sea power and the US Navy. Because without its navy, which has been the most powerful in the world for the past seven decades, the United States could not have been as active a participant in the world as it has been. Or, to take a less charitable view, the US could not have become embroiled in or caused as much trouble as it has.

Two salient facts that reflect the power of the US Navy are that it has ten operational aircraft carriers, compared with only seven spread among all the world’s other navies. And the navy’s $160 billion budget is, by at least one measure, more than China spends on all the branches of its military combined— and China spends more on its military than any country in the world except the United States. But ships and budgets are only part of the equation, for sea power takes many forms and has many elements, and there is considerable disagreement over what these are and how they correlate. Even defining sea power is not all that easy. For the American apostle of sea power, Alfred Thayer Mahan, writing in 1890, it was ‘in its broad sweep all that tends to make a people great upon the sea’. A century later, the US Navy identified it as ‘the sum of a nation’s capabilities to implement its interests in the ocean’, which aligns well with naval historian Geoffrey Till’s view that commanding the sea ‘means you can use it for your purposes’– trade, fishing, mineral extraction – ‘and prevent the enemy from using it for his’. A lot hangs on the shift in focus from ‘upon the sea’ to ‘in the ocean’.

Mahan enumerated six ‘principle conditions’ or features that determine whether a country can become a sea power: geographical position or location; physical conformation, including the nature of the sea coast, its agricultural and mineral wealth; how big it is; the size of its population; the ‘Character of the People’; and the ‘Character of the Government [and] national institutions’. This list seems to derive from Mahan’s assessment of the features that accounted for Britain’s place as the world’s foremost naval and commercial maritime power at the end of the 19th century. His reference to the character of the people and governmental institutions – constitutional rule implemented by people of Anglo-Saxon origin and favourably disposed to free trade – clearly suggested the potential of the United States to join Britain’s ranks.

In this connection, it is worth pointing out that with respect to the geo-side of this geopolitical formulation – location, the lie of the land, area, and population – Great Britain and the United States resemble neither each other nor any other country or empire with a clear claim to having exercised sea power. A more balanced and historically grounded assessment shows that sea power requires three basic ingredients: money, and lots of it; a direct interest in sea-based trade; and enemies, real or imagined.

Of these elements, the easiest to account for is money, or national wealth. Generally speaking, ships are the most technologically sophisticated and robust machines produced by any given generation of human society, and the complexity and expense rises exponentially when it comes to warships. Going back to those American aircraft carriers, each of them is a nuclear-powered floating city of 5,000 people with a world-class airport. Though less versatile overall, nuclear-powered submarines – capable of circumnavigating the world entirely underwater and of launching nuclear-tipped ballistic missiles at targets more than 7,000 kilometres away – are just as sophisticated and awe-inspiring.

As the financier JP Morgan reportedly told someone who asked about the cost of one of his yachts: ‘If you have to ask, you can’t afford it.’ In a similar vein, if a country has to think too much about what an appropriate naval budget might be, it probably lacks the wherewithal to develop anything more than a deterrent naval force. This is no small thing. Sweden is poised to increase its defence spending substantially in response to the changing geopolitical environment around the Baltic. But bolstering a nation’s naval defences and developing a sea power capable of promoting its national agenda half a world away are entirely separate undertakings.

The second tine of the sea power trident is maritime trade. In Mahan’s view, the point of sea power was to maintain freedom of trade – or at least to ensure unfettered commercial exchange for oneself – on the oceans the world, which he described as ‘a great highway; or better, perhaps… a wide common’. This formulation was upended by a slew of 20th-century technological and legal developments that have quite confounded our ideas of what constitutes trade and that have called into question the virtues, and the practicality, of considering the sea as a kind of global common.

Traditionally, when people spoke of protecting their trade, they meant trade carried in ships that flew their country’s flag. One of the more disruptive developments of the 20th century was the rise of the flag of convenience, by which the beneficial owner of a ship can register it in a country with less stringent labour laws, lower labour costs, and a more lax regulatory environment generally. This has led to an unprecedented rise of shipping companies that cater to markets outside their home country. The two biggest flags of convenience registries are Panama and Liberia, which together account for more than a quarter of the world’s shipping. Yet neither Panama nor Liberia has, or aspires to have, a navy, because neither country has a real stake in the thousands of ships that fly their flags.

But what of the world’s two leading economies, China and the United States? China has the largest fleet of merchant ships owned and registered in the same country; more than a quarter of its international trade is carried in Chinese-owned ships, and efforts are under way to increase that proportion substantially by acquiring new ships, whether built at home or abroad. By contrast, only 2 per cent of US foreign trade is carried in ships built in the United States and flying the US flag. Thanks to ancient protectionist legislation intended to preserve shipbuilding jobs, that number is unlikely to increase in the foreseeable future.

If a navy’s primary purpose is to protect its country’s trade, and if a sizeable proportion of that trade is carried in ships owned and registered in that country, common sense dictates that it should have a navy. This is one clear-cut reason for why China wants to develop a blue-water force—and it is because of that trade that it can afford one. However, if one is dependent on trade carried in ships that are foreign in all respects, as is the case with the United States, the traditional rationale for a navy is less compelling. Some 98 per cent of US trade is carried in ships belonging to foreign owners, often flying the flag of a third nation, commonly manned by crew hailing from yet other countries. How, then, does one define a nation’s interest in that cargo or that ship, its crew or its owners, especially when the biggest threat to such a dependency might be a trade embargo by foreign shippers. No navy can coerce shippers into moving goods which they don’t want to handle.

The globalised nature of the shipping industry, as reflected in the practice of transnational ownership and reflagging, has deep political implications that the word ‘globalised’ glosses over. Most people seem to view the connectedness fostered by global shipping as a net positive. At the same time, the shipping industry is perhaps better described as deracinated, or yanked up by its roots. And it is only by acknowledging that transnational enterprises like shipping are fundamentally rootless entities that we can start to rationally reconsider their place on a nation’s agenda, starting with whether they merit the protection of that country’s navy.

Another rationale for a navy is concern about what the US Navy calls a nation’s ‘interests in the ocean’. But, as cartographers are wont to say, ‘Here be dragons’. These ill-defined interests are at least as old as Hugo Grotius’s Mare Liberum (1609). While this treatise on international law ostensibly concerned the freedom of the Dutch to trade in southeast Asia, many contemporaries thought it had as much to do with preserving the Dutch right to fish on the Dogger Bank in the North Sea.

The voyage to the bottom of the sea began with the unilateral Truman Proclamation of 1945, which asserted that, to promote the extraction of ‘petroleum and other minerals… the Government of the United States regards the natural resources of the subsoil and sea bed of the continental shelf’ subject to US ‘jurisdiction and control’. This concept of an exclusive economic zone (EEZ) was confirmed by the United Nations Convention on the Law of the Sea (UNCLOS) in 1981.

There are many disputes over delimiting EEZs, but no region has been more hotly contested than the South China Sea, where China is pushing the limits of international law, and credibility, by creating artificial islands around which it seeks to assert maritime claims. This is happening within the boundaries delimited by the ‘nine-dash line’, which first appeared on a map published under the auspices of the Nationalist Chinese government in 1947. The United States raised no objection to the nine-dash line when it was first drawn, and it has been slow to challenge the line’s legitimacy, partly because the nationalist government in Taiwan believes that the line delineates its legitimate claims in the region, and because, while the People’s Republic of China (PRC) adopted the same view, until recently they had neither the will nor the means to enforce it. This has resulted in a tepid response to Chinese assertions, even as late as 2014, when a State Department official testified to the US House Committee on Foreign Affairs that ‘any use of the “nine-dash line” by the PRC to claim maritime rights not based on claimed land features would be inconsistent with international law. The international community would welcome China to clarify or adjust its nine-dash line claim to bring it in accordance with the international law of the sea.’

The PRC is now advancing its claims, partly to secure petroleum reserves beneath the South China Sea, but also in the interest of controlling access to fishing grounds, which are under immense pressure from Chinese fishermen. The situation can be summarised in a handful of numbers. Between 1950 and 2013, the reported volume of wild fish landings worldwide rose sevenfold. In that time, the Chinese share of the catch grew from just 4 per cent to 32 per cent. This helps explain why the share of fish caught by Asian nations grew from less than a third to more than two-thirds of the world total in the same period. The increase in China’s share has been a relatively recent phenomenon, and between 1979 and 2013 the number of Chinese fishing vessels grew from 52,225 to 695,000, a 13-fold increase. China’s coastal fish stocks have been devastated in the process, and this is a major reason that China is paving over reefs and islands in contravention of UNCLOS rules on artificial islands, at enormous but largely unacknowledged harm to the environment and at the risk of creating actual enemies out of potential ones. This brings us to the third prong of the sea-power trident, the role of the adversary in naval strategy.

As the centennial of the First World War reminds us, paranoia is a great stimulant for military spending. The naval arms race between Germany and Britain was among the more visible and expensive manifestations of the fear coursing through the veins of Europe’s body politic around the turn of the 19th and 20th centuries. It was reflected in part by the astonishing growth of the German merchant navy, whose North German Lloyd and Hamburg-America Line were the world’s largest shipping companies, and had global reach. British shipping companies tended to focus on specific regions and routes.

There are many ways to consider the origins of the First World War, but to simplify our analysis of the naval competition, it is helpful to consider Anglo-German rivalry in terms of whether those nations’ respective navies were intended for defence, aggression, or prestige.

Reputation and status cannot be discounted as a factor in the development of sea power. Whereas navies intended for defence or attack are created with a specific enemy or enemies in mind, prestige navies are instruments of propaganda – from the fleets of the Hellenistic age, to the Ming dynasty ships that sailed under Zheng He in the 15th century, the 17th-century Swedish flagship Vasa, ‘a powerful propaganda weapon emphasising Gustav Adolf’s right to the crown’, and on to the Edwardian era. There is, of course, considerable overlap between navies as practical instruments of war and as symbols of national pride, but evaluating the rationale for naval expansion across Europe, and not just in Britain and Germany, a century ago in these terms might be a productive exercise.

What of China’s well-known ambition to expand its navy today – or of the less thoughtfully scrutinised ambition of the United States to meet all comers, regardless of cost? There is much in favour of sticking with the status quo, especially if that status quo leaves one’s pride untouched, as would be the case for the United States. A decade ago, admirals and historians began to develop the idea that the world’s navies might be in transition between ‘modern’, or traditional, notions of national sea power and a ‘postmodern’ collaborative approach more focused on maintaining the flow of goods so essential to contemporary globalisation. The prospects for such collaboration now seem less bright. And unless the logic of naval development is rewritten, China’s quest for naval self-sufficiency and sea power rests on a solid, if traditional, foundation.

In 2001, a Chinese analyst laid out the various reasons his country might want to develop its navy, regardless of the international resistance that it might provoke. He wrote: ‘If the unfavourable maritime situation is allowed to continue deteriorating, if we continue to be surrounded in our coastal waters, then how can we speak of China rising to prominence? How can Chinese naval power be promoted? How can China’s maritime rights and interests be guaranteed? How can a country with just a “brown water” navy win the respect of other countries for its naval power’?

What is most fascinating about this brief passage is the degree to which it seems to echo the opinion of an American writer on the same subject: ‘There is a rank due to the United States among nations which will be withheld, if not absolutely lost, by the reputation of weakness. If we desire to avoid insult, we must be able to repel it; if we desire to secure peace, one of the most powerful instruments of our rising prosperity, it must be known that we are at all times ready for war.’

That is how George Washington, the first president of the United States, couched his appeal for a navy in his fifth address to Congress, in 1793. All things being equal, Washington could at the very least appreciate China’s current geopolitical predicament. More difficult to fathom is how he would square the US position as the world’s pre-eminent naval power with his admonition to ‘steer clear of permanent alliance with any portion of the foreign world’.

This essay originally appeared under the title ‘Elements of sea power – past and present’ in ‘The Return of Geopolitics’, Bokförlaget Stolpe, in collaboration with the Axel and Margaret Ax:son Johnson Foundation, 2019.