The Importance of Being a Corvette

A trivial question for serious navies.

Journalist Jarmo Huhtanen of Finnish daily Helsingin Sanomat stirred up a little controversy yesterday, by publishing an article where he lays out the case that the Pohjanmaa-class corvettes in the form they were ordered in are not corvettes at all, but frigates.

Now, at the outset it has to be noted that Huhtanen is probably the single most experienced and knowledgeable defence journalist employed by any Finnish non-specialised media, and he has been covering the Pohjanmaa-class from its humble beginning as the MTA 2020. As such he is well-placed to raise the question, and he certainly has some points.

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The whole Squadron 2020 in the Finnish archipelago. The Finnish Navy needs to be able to perform surface combat, ASW, convoy escort, and mining missions year-round in any kind of weather, something that dictate the need for larger multipurpose vessels than currently in service. Source: Finnish MoD

It is certainly true that the vessels have grown throughout the project. The original size was given as about 90 meters back in 2015. This now currently stands at 114 meters, a sizeable increase. It is also true that the size makes it questionable whether the vessels really are “the most capable corvettes in the world”, as commodore Harju stated, or more accurately “decently sized frigates”. Huhtanen also notes that internationally the classification of surface warships is imprecise and partly overlapping when it comes to tonnage.

Let’s address the first part first. While it is impossible for an outsider to know exactly what has been going on behind the scenes, as the Navy has been notoriously tight-lipped about the details of the project. In general terms, having seen and been part of a few vessel design projects I can note that it isn’t rare for a vessel to grow between design iterations. The reasons are many, but in general it is better to start small, as smaller generally means cheaper, and then to add space once it is clear it really is needed. Considering the lifespan of the Pohjanmaa-class, room for growth is also a serious considerations, and something which often in hindsight hasn’t been emphasised enough on military vessels (see Hamina-class going from 57 mm to 40 mm deck guns to save weight during MLU). Bad planning on the part of the Navy? Not necessarily, it might just be the correct decision once the detailed design has matured.

At the same time the fixed budget has grown by 8 %. As I noted in my last post, the total still seems very low, although direct comparisons with other similarly sized ships are difficult to make. MoD Kaikkonen attributed the increase to an increase in the budget for the building of the ship, something that naturally correlates with an increase in vessel size. This obviously again raises questions about the quality of the information available upon project launch and what happened between 2015 and today, but in the grand scheme of things (remember that the oft-quoted 1.2 Bn Eur isn’t the full project cost, but rather only the additional funds allocated outside of the normal FDF budget) I find it difficult to be overtly excited if the budget overruns stay at this.

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The last time around Finland operated frigates, they were called ‘escorts’ (‘saattajat’). While there certainly were political considerations behind the designation, it does in fact also align with older nomenclature. Source: Esquilo via Wikimedia Commons

Huhtanen’s article include a few rhetorical leaps I don’t quite follow or agree with. One thing is the comparison to the Swedish Visby-class, and noting that they are 40 meter shorter than the Finnish vessels and significantly lighter (Visby being rated at 640 tons). The comparison is about as useful as comparing the specifications of our new K9 self-propelled howitzers to those of the Swedish Strv 122 tanks. Yes, both vessels are grey, sail the seas, and are called corvettes, but the design concepts (and the doctrines behind these design concepts) are different enough that a direct comparison is of little use. I have earlier written about the topic over at the blog of the Royal Swedish Academy of War Sciences, but in short compared to Pohjanmaa the Visby trades ice-going capabilities, air-defence missiles, mining capability, a helicopter hangar, and economics for stealth and speed. Neither approach is wrong, but they are very different and stems from the different concepts of operations the Swedish and Finnish Navies employ. However, it can be noted that the Swedish plan is that the next series of surface vessels will grow, even if they will still remain significantly lighter than the Pohjanmaa-class.

Mentioning that the Pohjanmaa-class are of the same displacement as the Freedom-class LCS is to be considered a red herring, and Huhtanen himself notes that this is likely a coincidence. An old article from 2016 by Olli Ainola is also linked, and while Ainola was no mean writer when it came to defence topics, that particular article was frankly little more than a hit piece, which I discussed in detail shortly after its publication.

I still hold it likely that if the Pohjanmaa-class eventually join the Navy in the shape currently envisioned and under the adjusted budget, the Finnish Navy will not only operate the strongest single warships currently based in the Baltic Sea, but they will do so at a bargain. I do fear that there is a risk that the budget is still too tight, and that some key systems will be ‘fitted for but not with’. However, the Navy has so far shown to be able to focus on the important, and make the cuts where they will least impact the effectiveness of the vessels. The Finnish concept of operations is also clearly visible in these compromises, such as the small calibre of the main gun (the vessels aren’t expected to provide naval gunfire support) and the decision to go with a medium-range air defence system as opposed to trying to fit a long-range bluewater system. Importing the combat systems and having an internationally established defence supplier provide integration will also significantly reduce the risks associated with the project, as the combat systems package is almost certain to be the weakest part of RMC’s know-how. In the end, the Pohjanmaa-class is clearly intended as a fighting weapon, and not as a fleet in being as Huhtanen suggests. They will play an important part in deterring hostile aggression throughout the spectrum from peace to war, and in doing so provide a flexibility found in few other systems. Their main issue is the low number, which causes redundancy issues and makes them vulnerable to losses.

But are they really corvettes?

During the age of sail warships were simply rated by how many guns they had. Granted some where faster than others, and some had longer endurance, but in the end you could simply count the number of guns and tell if something was a frigate. Both the corvette and frigate designations date to these times, with the dividing line between the corvette and the frigate usually being drawn somewhere between 20 and 30 guns.

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A painting by Christoffer Wilhelm Eckersberg depicting “A Danish Corvette Laying in order to Confer with a Danish Brig”. Source: Wikimedia Commons

Then came the steamships and a requirement for more specialised roles. The advent of submarines and aircraft created the modern three-dimensional naval battlefield. The first modern corvettes were the British Flower-class, which were light ships intended to escort convoys and fight German U-boats on the Atlantic, and not much else. The frigate designation also saw a renaissance during WWII, as the Royal Navy started calling their slightly larger subhunting convoy escorts for frigates. Confusingly enough, the same kind of vessels were designated destroyer escorts by the US Navy, and the Royal Navy also operated sloops which were roughly of the same size and capability.

After the war things got still more confusing. Generally vessel sizes grew, and suddenly there were cruiser-sized ships hunting submarines. But since cruisers don’t hunt submarines, these were clearly just very large destroyers (except in the Soviet Union, where they were “large anti-submarine warfare ship”). At the same time more and more navies started to move away from single-purpose ships to multipurpose ones. Developments such as increased range for aircraft and the lower number of available hulls meant that ships expected to operate in narrow seas such as the Baltic Sea no longer could count on being able to choose which kinds of enemies they could encounter (for armoured people, this is pretty much the same kind of development pattern that eventually brought us the main battle tank to replace different armoured fighting vehicles tailored for different roles).

Long story short, today multipurpose vessels start with corvettes being the smallest, then moving up in size through frigates and on to destroyers. Where exactly the lines are drawn is an open question, and also varies with country. In US nomenclature, FFL (the abbreviation coming from “frigate, light”, in itself an interesting statement) designates a corvette, which is between 1,000 and 1,500 tons full load displacement. In Europe, any warship larger than a patrol craft but smaller than a frigate can be called a corvette, if the navy in question is so inclined. Frigates are between 1,500 to over 6,000 tons full load displacement according to USNI, who also note that due to “internal political reasons”, some navies mislabel their frigates as destroyers, or vice versa. This is often based on budgetary considerations and/or naval traditions. Here it could be noted that if one has received budgetary funds for a corvette, and is from a country that traditionally only operate lighter surface combatants, any vessel straddling the corvette/frigate-line would likely be designated a corvette for political reasons. Conversely, the British Type 31e, the low-end frigate in their high-low frigate mix, at times during the tendering process looked closer to a high-sea corvette than a frigate. But since it was designed to compensate for a shortfall in the number of frigates, and since the visuals of having cut the funding of the Royal Navy to the extent that they were buying corvettes instead of frigates didn’t fit British politics, they have never officially been described as anything but “affordable” frigates.

In the end, Navies can usually get away with calling their vessels more or less what they want, and generally these designations have been accepted by the outside world. The British Type 45 are destroyers, but their cousins in the Horizon-class in French and Italian service are frigates.

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Formerly known as a “coastal corvette”, the 400-ton HMS Sundsvall (K 24) is today known simply as a corvette in Swedish nomenclature. Here visiting Kokkola in 2010. Source: Own picture

However, simply discussing displacement doesn’t give the whole picture, as much is related to the capabilities of a vessel. Yet another factor is that some countries have doctrines differing from established western thinking to the extent that the vessels these result in aren’t possible to fit in any of the given designations. You can get entertainment for a whole evening if you can get two naval historians with opposite views arguing over whether the German WWII-era Scharnhorst-class are battlecruisers or battleships, an issue that stems from the battlecruiser and battleship division being based on British vessels. The Soviet large anti-submarine warfare ship has been mentioned already, but the Soviet and Russian Baltic Fleet has also seen e.g. the Project 1234 Ovod (Nanuchka-class in NATO-parlance), which is a “small missile ship” if you ask the Russians, and either a fast attack craft or a corvette if you ask the West. A key issue here is the size and endurance which makes it corvette-like, but the lack of any serious armament except a heavy anti-ship missile battery is generally seen as a defining feature of a FAC. Another interesting case from the Baltic Sea is the Swedish Navy, which used to operate 400-ton vessels with significant capabilities in all three dimensions, but sacrificed endurance and seakeeping capabilities in doing so. These used the Swedish designation kustkorvett, or coastal corvette, but since the late 90’s the surviving vessels are simply called corvettes. The 250-ton Hamina-class will provide something along the same lines post-MLU, being able to fight subsurface, surface, and air threats, but being too small to be classed as a corvette.

So what about the Pohjanmaa? The displacement is on the larger side for a corvette, the capabilities are at the very high end for being a corvette, and are in fact higher than many relatively modern frigates. Is there anything then that stops them from being frigates?

The one thing so far absent from the discussion is their shallow draught, which likely will lead to less than ideal seakeeping when operating in bluewater conditions. This is a compromise, and one which has been a hallmark for large Finnish-designed vessels for decades. Frigates are often associated with the open waters of the oceans, or at the very least the North Sea, and while Pohjanmaa certainly could hunt submarines in the GIUK-gap, that’s not where she will be able to play to her strengths. Instead, that would be in the narrow waters close to the shores of the Baltic Sea, waters more often associated with, well, corvettes. However, living in a stable does not make one a horse, at least not in and by itself.

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Is it a frigate? Is it a corvette? Is it a minelayer? Yes, and no, on all three accounts. Source: Finnish MoD

Is she then a frigate? I personally would have to answer with “Yes, but not that kind of a frigate.” Designating her a corvette isn’t necessarily wrong either, but that would also have to be accompanied by the same asterisk. Ironically, it does seem that today’s Pohjanmaa-class will inherit not only the name but also a difficulty in straightforward classification from the original Pojama-class of the late 18th century. I guess we’ll simply have to resurrect the phrase “archipelago frigate”.

4 thoughts on “The Importance of Being a Corvette

  1. :)

    I personally see frigates as larger general-purpose vessels, capable of completely independent operations in blue waters, whereas corvettes are mostly ASW/ASuW capable, but lack proper air-defence due to their size and are meant to operate mainly in green water areas.
    Destroyers would be very large and heavily armed land-strike and/or area air-defence capable ships.
    Thus, I’d view Pohjanmaa as a frigate, fulfilling mostly corvette roles.

  2. Pingback: What about us innocents? – Maritime Defence Day 2019 – Corporal Frisk

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