The possible outcome of the review of the Royal Australian Navy’s surface combatant fleet has generated a fair amount of public commentary, some of which has focused much too closely on specific solutions. In particular, there has been much comment about so-called corvettes, with some commentators making a rather surprising leap from the high-level geopolitical and economic drivers outlined in the 2023 defence strategic review to the specific offerings of particular suppliers. There’s a very wide logic space to be traversed before any solution can be arrived at, and in this article I hope to map some of it out.

The navies of the geopolitical network with which Australia and New Zealand are aligned are faced with the reality that they are numerically overmatched by their potential adversaries. Not even the United States can afford to address this overmatch with sophisticated multi-function ‘Tier 1’ combatants; a doctrine known as ‘distributed maritime operations’ has evolved to address this reality.

DMO spreads the combat power of a naval force over both high-end multi-function combatants and large numbers of less capable and more affordable platforms. Larger numbers increase the deterrent value of a force because they complicate the aggressor’s targeting problem. More ships have to be found, identified and targeted by the aggressor, increasing the likelihood that sufficient numbers will survive the aggressor’s first strike to impose an unacceptable cost in retaliation.

Successive US Navy chiefs of naval operations have put DMO at the heart of future doctrine. I suspect the DSR’s reference to ‘smaller, cheaper’ surface combatants may have been informed on some level by DMO principles; the presence of retired US Admiral William Hilarides on the surface fleet review should ensure that they are taken into account.

For the Tier 2 concept to work, it must be possible to acquire sufficient platforms for the DMO concept to become operable. That means they must be affordable. Affordability must be viewed on a whole-of-life basis, which means that it must be possible to manage obsolescence without the very expensive, time-consuming and risky mid-life upgrades to which both the Adelaide-class and Anzac-class frigates were subjected. Above all else, the spurious linkage between platform size and affordability that tends to dominate discussion on naval force structure must be discarded, and the sooner the better.

Last month in the Strategist, Rear Admiral Rowan Moffitt described ^[1] the geographic and oceanographic realities that make arbitrary size limits (such as those linked with what are sometimes described as corvettes) utterly inappropriate for Australian conditions. Australian and New Zealand naval combatants, whether Tier 1 or 2, require range, endurance, seakeeping, habitability and aircraft operating characteristics that are inconsistent with such limits. To my knowledge, this was the first contribution to the public discussion from a senior naval practitioner, and it provides a very necessary counterweight to other recent commentary.

There’s a rapidly developing concept in naval force design that should have a significant influence on Tier 2 capability choices—modularity. A modular ship is essentially a standard platform able to receive capability ‘modules’ tailored to the needs of specific operations. Modules are based on standard containers that might include anti-submarine warfare sensors, autonomous vehicles for mine countermeasures, long-range surface strike missiles or other specialised capabilities. Modules are integrated with the ship’s physical and computing architectures by standardised interfaces to digital backbone systems, electrical power, cooling systems and ventilation.

The benefits of modularity include both operational flexibility and efficient obsolescence management, because capability is upgraded by replacing modules. The availability of the ship itself is unaffected by the upgrade; it remains available for operations that don’t require the module that is being upgraded.

A full description of the pros and cons of modularity would require a much longer article than space allows, but recently published Royal Navy operating concepts ^[2] put modularity at the heart of future fleet design. Some commentators point to the US Navy’s littoral combat ship as an instance of the failure of modularity, but problems ^[3] with the LCS stem largely from the untested nature of the entire concept (not just the modular aspects) at the time the green light for procurement was given some 20 years ago, and engineering problems with one of the two variants.

Lessons learned from the LCS program have made modularity more workable, not less. However, modularity should be approached with a large measure of healthy scepticism, and the concept must be subjected to modelling and serious technical study before its adoption is seriously considered. It must also be noted that as yet there are no modular combatants of the level of capability described in the Royal Navy operating concepts in service or even at an advanced design stage. This level of capability is several stages more advanced than existing modular combatants, including the LCS and the Danish STANFLEX combatants.

Maintaining a steady naval shipbuilding drumbeat is essential to the viability of this strategically vital industry. However, that is not sufficient justification for proceeding straight to a convenient off-the-shelf solution. Geopolitical drivers must be integrated with emerging doctrine, technological opportunities, and geographic and oceanographic realities to arrive at a set of requirements against which the entire range of potential solutions can be assessed.

It may well be that the depth of local naval architectural, systems integration and engineering talent that has been built up over the years make it possible to consider a home-grown solution, de-risked by thorough testing, simulation and prototyping, and by adopting proven propulsion, generation and digital backbone systems and combinations. At the very least, such an option must not be ruled out. That said, both the Australian and New Zealand navies have benefited from operating ship types in service with the US Navy and Royal Navy. Parent navy design authorities have greatly simplified configuration management, and access to common supply chains has simplified sustainment. These advantages mustn’t be lightly dismissed.

The usefulness or otherwise of the ‘Tier 1’, ‘Tier 2’ terminology has been questioned. It has been pointed out ^[4] that these are not capability descriptors; naval forces are assembled according to the capabilities required by the mission at hand, not by arbitrary capability tiers. It is critical to note that these tiers are only useful in programmatic terms, in that they offer a convenient means of distinguishing between high-end, multi-function combatants like the current Hobart-class destroyers and the future Hunter-class frigates and what at this stage is a purely theoretical, less capable and thus less expensive combatant type that can be acquired in greater numbers.

To summarise, Tier 2 combatants must be sufficiently affordable to be acquired in numbers. They must be large enough to operate in the full range of geographic and oceanographic conditions arising from Australia’s strategic circumstances. They must be adaptable through life as strategic circumstances and naval missions evolve, and they must be capable of adaptation and upgrade without costly, lengthy and risky half-life upgrades. Modularity in design and operation may offer distinct advantages, but capability must be defined without regard to arbitrary type classifications. Labelling the Tier 2 combatant as a corvette and allowing that label to define the solution space is unhelpful, to put it mildly.

My interest in the Tier 2 discussion is easily explained. The timeframe for life-of-type expiry of the patrol and combat elements of the New Zealand naval fleet corresponds with the approximate timeframe for the likely Australian Tier 2 program. A combined Australian–New Zealand program would make sound economic sense for both countries while enhancing operational complementarity. Modularity would allow each navy to adapt its Tier 2 ships to its own needs while operating the same platform systems and digital backbone.

The outcome of the surface fleet review will no doubt be awaited with great interest on both sides of the Tasman.