The structure of a country’s naval fleet should reflect the thinking of governments (and navy) about their use of the sea. To a large extent it’s possible to ‘reverse engineer’ naval aspirations from the force structure. For example, true blue water capability requires long endurance, which in turn means larger vessels and/or the ability to replenish them at sea. As well, blue water forces often operate with the support of long-range maritime patrol aircraft. Conversely, navies intended to predominantly operate closer to home have a preponderance of smaller (and hence shorter-ranged) vessels for littoral operations, and there is less emphasis on replenishment vessels and long-range air support.

No surprises there. But we can quantify some of these observations, and when we do, some interesting results pop out. During his time at ASPI a while back, then intern Tonmoy Dutta-Roy (who’s now doing his bit to alleviate navy’s shortage of engineers) came up with a simple but interesting method of measuring the shape of a navy. His insight was to note that priorities are obvious when you look at the ratio of various parts of the fleet—the number of major combatants divided by the number of minor combatants, being one example. Or the number of maritime patrol aircraft divided by the number of major combatants etc. Of course, anything worthwhile in the defence world needs a three letter acronym, so these ratios are called Force Structure Indices (FSIs).

Let’s see how this works by looking at various nations’ blue water aspirations. Here the USN is supreme—there’s no other navy capable with its power projection capabilities (or that’s even close). So we’ll use the USN as a benchmark against which we measure the capabilities of other navies. The results are in the table below.

Table 1: Force structure indices for selected navies. (Data source: Jane’s Fighting Ships)

(There’s nothing magic about the set of FSIs shown in the table. To get, for example, the ratio of amphibious ships to oilers, you can just divide the numbers in the third row by those in the fourth.)

To see how to use FSIs, let’s start by comparing the USN with the navies of two rising powers—India and China. These two countries, although often mentioned in the same breath as aspirant naval powers, are actually at very different stages of naval force development at the moment. Consistent with its stated ambition, India’s navy is in the process of being developed as a blue water force ^[1]—and the change in the ratios between the current fleet and that of just a few years from now will move India closer to the USN benchmark. But note that the FSIs don’t tell you anything about absolute numbers and hence overall capacity; the Indian navy is still a long way short of the USN’s overall capability.

China’s navy, on the other hand, is entirely different. Compared to India it has a lot more minor vessels and amphibious ships relative to its fleet of major warships, and there aren’t many maritime patrol aircraft or at-sea refueling vessels. In short, it looks nothing like a navy that has been built for blue water operations. Instead, it’s entirely consistent with a long-term focus on operations across the Taiwan Strait and in waters close to the Chinese coast. Rather than long-range forces, they’ve focused on short-range forces that, when employed with other systems such as missiles ^[2] and sea mines ^[3], can conduct local sea denial operations—keeping external powers at bay. And the number of amphibious ships provides a credible capability against nearby territories—especially Taiwan. If, as many predict, Chinese naval ambitions expand outwards, the ratios in the table should start to migrate towards those of the blue water archetype of the USN.

Closer to home, there’s a striking coincidence between the numbers for the RAN and the USN—the FSIs are essentially identical in the categories where sensible comparisons can be made. At first blush that seems a little puzzling—the global strategic posture and reach of the United States is quite different to the locally-focused ‘defence of Australia’ notions that have underpinned our defence policy for decades. But while it might be tempting to put it down to ‘USN envy’ driving our decision making, ultimately it’s Australia’s continental geography that’s decisive.

Andrew Davies ^[4] is senior analyst for defence capability at ASPI and executive editor of The Strategist. Thumbnail image courtesy of Flickr user Royal Australian Navy ^[5]. ^[6]