The aircraft carrier is possibly the most misunderstood modern warship, and a lot of nonsense has been written about them.
So, here are a couple of very important points that are not generally known (outside of specialists) or are often forgotten.
Aircraft carriers are difficult to detect.
Perhaps more importantly, they are difficult to identify. Regarding the difficulty of detection, the seas are very big and, in comparison, even the biggest of aircraft carriers are very small. Modern maritime patrol aircraft (MPA) have radars that have ranges of hundreds of nautical miles (nm) but oceans extend for thousands of nautical miles.
Moreover, radar impulses can be detected by electronic support measures (ESM) systems at significantly greater range than the radar can detect the platform (air or surface or even submarine) carrying the ESM. In wartime, an MPA using its radar gives itself away, opening the way to it either being intercepted and shot down before it can locate the carrier, or to the carrier simply altering course and avoiding the MPA.
Of course, MPAs also have ESM, but this works only if the carrier and its task group (Carrier Battle Group: CBG) are emitting electromagnetically.
But if the CBG has adopted strict electromagnetic silence (and it can do so & this is exercised), then there is nothing to detect. So the MPA is reduced to the Mark 1 eyeball as its only useful sensor.
And that is very short-ranged indeed. (Perhaps an MPA might try to deploy passive sonobuoys to hear CBG noise radiated under water: but this too, faces problems, to be discussed below.) Just because a carrier has airborne early warning & control (AEW&C) aircraft does not mean that these will be flown all the time or that their radars will always be turned on. So they cannot be relied on to give ESM data.
As for spy satellites, it is truly depressing the amount of well educated & intelligent people that take Hollywood film & TV nonsense about these assets seriously.
Spy satellites have very serious limitations (which is why the US invests so much in alternative strategic reconnaissance platforms).
Visible spectrum spy satellites can’t see through cloud (and there is a lot of cloud about . Infra-red & radar spy satellites can be confused, misled and jammed by the same technologies that counter their surface and airborne counterpart systems.
To achieve high resolution spy satellites must orbit at low altitudes.
Their swath width (the width of the Earth’s surface that their sensors cover) is consequently narrow. Each spy satellite has a fixed orbit, and the orbits of all spy satellites are known. Thus, naval, military and air commanders will know when a satellite will overfly their forces and so can initiate countermeasures and deception activities before the satellite rises over the horizon and cease them when it drops below the horizon. Satellite overflights of any particular part of the globe can be measured in minutes.
Conversations and interviews with personnel of the Space Operations division of the South African National Space Agency regarding the country’s low Earth orbit (LEO) Sumbandila Earth observation satellite, which orbited at an altitude of 500 km, indicate that an overflight (of mission control, at Hartebeesthoek, west of Pretoria) took about 15 to 20 minutes and happened once a day. And spy satellites must also use LEO. And once a spy satellite has obtained its images, it must downlink them. And they must then be analysed by specialist interpreters.
Of course, the more spy satellites you have, the more overflights you get.
But spy satellites are scarce.
Yes, there are submarines.
These can listen for carriers and CBGs with long-range passive sonars. However, there is a lot of background noise in the sea, much of it natural. As Admiral Sandy Woodward has pointed out (1992: ‘One Hundred Days’ Harper Collins, London, p. 47) sea creatures “can be a rackety lot” and described the background noise experienced by passive sonar as “cacophony”.
Jim Ring (2001: ‘We Come Unseen: The Untold Story of Britain’s Cold War Submarines’ John Murray, London, pp 136-137) related the story of how, in 1977, while on exercise, the RN SSK HMS Orpheus was trying to locate (& then attack) the USN CV (not CVN) USS John F Kennedy. The SSK found the CV because the sub’s ESM detected radar emissions from an aircraft radar being tested on the carrier.
It could not find the ‘JFK’ using sonar because, Ring reported, “[t]here were no sonar contacts, so if the carrier was there she was moving only slowly, thereby reducing her sound signature to avoid detection.” Of course, passive sonar performance (especially data processing) has improved hugely since 1977 but you can be certain that sound emission reduction from US (& other) carriers has also improved hugely as well. Moreover, sonar is a complicated thing: except at short ranges, sound does not move in straight lines under the sea. Passive sonar can detect a vessel 60 nm away but not one that is only 25 nm away.
(Figures very approximate: only for rough illustration purposes.)
And then there are the effects of salinity layers and thermoclines, which can also affect submarine sonars.
Carrier Captains and CBG Admirals have more options than generally realised. And strategic deception hasn’t been mentioned yet!
While strategic deception is central to the Chinese art of war, it is equally central to the British art of war. If anything, the British might be better at it. Deception is also important in Japanese military & naval history & the US has successfully used strategic deception as well. Tactical deception will be discussed below.
What is generally not grasped outside the major navies is how difficult it is to identify an aircraft carrier. Let us return to Admiral Woodward’s memoirs (pp 209-210).
“[T]he Royal Air Force …. had alerted us urgently to the Argentinian aircraft carrier which they pin-pointed for us, well out to sea. Fortunately, I knew perfectly well that it could not possibly have been the carrier, and in fact it turned out to be a large, harmless container ship, which can admittedly look very like a carrier to a Searchwater radar [carried by Nimrod MPAs] at times.” (I have long been fascinated by the failure of so many to grasp the significance of this passage.) Much more recently – in the Winter 2014 edition of the US Naval War College Review – retired Russian Navy and Coast Guard officer Lt-Cmdr (Captain III Rank in Russian terminology, I think) Maksim Tokarev wrote in his paper “Kamikazes – the Soviet Legacy” (p.77) that “knowing the position of the carrier task force is not the same as knowing the position of the carrier itself.
There were a least two cases when in the centre of the [USN CBG] formation there was, instead of the carrier, a large fleet oiler or replenishment vessel with an enhanced radar signature (making it look as large on the [Tupolev TU-22M] Backfires’ radar screens as a carrier) and a radiating tactical air navigation system. The carrier itself, contrary to routine procedures, was steaming completely alone, not even trailing the formation.” In short, carriers may look very different to other warships, but in radar cross-section terms, they look very like tankers, bulk carriers, car carriers and container ships. After all, they are all characterised by relatively small superstructures and long flat upper decks! There are only a few dozen aircraft and helicopter carriers in the world, but there are thousands of tankers, bulk carriers, etc.. Decoys will be plentiful and easy to arrange.
One final point in this section: again, a quote from Adm Woodward (also pp209-210).
The RAF “in mid-April  … signalled that they had located a group of fishing vessels in the precise spot I knew the forward [HMS] ‘Brilliant’ group was sailing. They reported the ships as fishing vessels, I imagine, because they were fairly close together, milling around on different courses, going nowhere in particular.” Remember Tokarev’s report of carriers outside their CBGs, and it is clear that Western CBGs and other naval task forces no longer sail in neat symmetrical formations like they often did during the Second World War.
Rather, in crisis, confrontation and war, they adopt deceptive formations and manoeuvres making identification difficult and (in wartime) dangerous.
Horses for Courses
Different countries use aircraft carriers for different missions. History indicates that, for the Royal Navy, aircraft carriers have had three major and equally important strategic roles: (a) air defence of the fleet, (b) to search, locate, engage, disrupt & destroy the enemy’s maritime warfare assets, whether submarine, surface or air, at sea or in harbour or in the air or on the ground; naval, air force or merchant; including key support infrastructure, and (c) provide air cover for expeditionary operations whether amphibious or not, for British and/or allied ground forces (and air forces while they set up their forward base infrastructure).
(a) Air defence of the fleet is the obvious precondition for the successful operation of the RN’s surface ships anywhere in the world. Carrier fighters allow surface ships to go nearly anywhere desired (although not necessarily on a sustained basis!) and greatly hamper hostile reconnaissance and surveillance operations. (The tactical mission is the interception of specific enemy reconnaissance aircraft or air raids.) This role includes air defence of convoys.
(b) To search and locate the enemy was the original mission for British naval aviation (the then Royal Naval Air Service or RNAS during the First World War). The first enemy maritime assets attacked by the RNAS were not warships but Zeppelins and their bases (in a number of land-based and sea-based raids in 1914). Likewise, the Fleet Air Arm (FAA) did not restrict itself to enemy warships but attacked, when possible, all elements directly connected with enemy maritime operations. It is well known that the first major warship sunk by air attack was the German light cruiser ‘Königsberg’ by land-based FAA Blackburn Skuas, in Bergen harbour, Norway, in April 1940. What is often forgotten is that the FAA Skuas made a series of follow-up raids during April and May, hitting other warships, destroying a supply ship (the explosions from which significantly damaged a mole, warehouses and cranes) and almost completely destroying several oil depots around Bergen. Other examples could be given. Second World War ASW operations by Escort Carriers and Merchant Aircraft Carriers also fall into this category.
(c) Air support for expeditionary operations includes air defence, air superiority, close air support and interdiction. This started, of course, with air support for the British Expeditionary Force in 1914, and has continued right down to and including Harrier and, latterly, helicopter operations in Afghanistan.
I have seen nothing that suggests these priorities have changed. Indeed, the concept of the Tailored Air Group is a clear statement that the ‘Queen Elizabeth’ class carriers will not have a single primary mission. Most navies with carriers use them in similar ways to the RN, although sometimes unable to match the full spectrum covered by the British.
There is, however, a big exception – the US Navy.
Up to the end of the Second World War, the missions of US Navy carriers were pretty much the same as those for RN carriers. But, post-1945, a new mission was developed: strategic bombing, using nuclear weapons. Of course, support of US expeditionary forces remained and remains an important mission. But the USN’s super carriers came into being to provide platforms big enough to effectively operate the large aircraft needed to carry the big and heavy atomic bombs of that period, far enough to threaten strategic (inland) Soviet targets.
These carriers and their bombers were part of the US national nuclear deterrent and massive retaliation force, long with the US Air Force’s Strategic Air Command.
This mission was subsequently transferred to the ballistic missile submarine force, but strategic bombing, albeit with conventional munitions, has remained the central focus of the US carrier force to this day. US carriers have been integrated into strategic bombing campaigns since at least Vietnam in the 1960s. A spin-off of this, as Captain Robert Rubel USN (Retd) has noted (“The Future of Aircraft Carriers” in the ‘Naval War College Review’ Autumn 2011, Vol. 64, No. 4), is that US administrations have come to use USN carriers as geopolitical chess pieces, “to demonstrate American concern, resolve or outright anger” (p.17). This is a striking development, because (if I remember correctly), in the time of their global dominance, the European powers almost never used their capital ships (ships of the line/ironclads/battleships) as such chess pieces. Rather, they used frigates/gunboats/cruisers (or even sloops) in such a role, even with other European powers. Capital ships were deployed either to show friendship or when war was expected imminently, and, in the latter case, an entire fleet would be deployed. As Rubel points out, the US “Navy and the nation are so used to operating carrier with impunity as airfields at sea that as new sea-denial threats emerge (as did the Soviet Navy) the potential for a role/risk disconnect is magnified” (pp17-18). In other words, using a carrier as a chess piece can put it in grave danger if the crisis turns into war (as the opponent-turned-enemy would know exactly where it was and could immediately attack it)
One of the consequences of these different mission sets for different navies is that aircraft carriers cannot be simplistically compared.
Their effectiveness lies not in how they relate to each other in, say, size, but how effective they are in fulfilling their roles within their respective national strategies. Those commentators who mock China’s first aircraft carrier because it is much smaller than its US counterparts are making a grievous error.
Before one can say carrier A is less capable than carrier B you must first know what carrier A is actually meant to do
There is a rather striking historical example of this. In the early 1970s, the RN carrier force was headed by the 50 000 t HMS ‘Ark Royal’ (then Britain’s only fast jet carrier), with an air group of 30 fixed wing types (including Phantoms and Buccaneers) and six helicopters.
The US carrier force was headed by the amost 90 000 t USS ‘Enterprise’ with an air group of some 95 aircraft (the USS ‘Forrestal’ and its sisters where not much smaller, each with an air group of 85). The all-weather bomber on the US carriers was the Grumman A-6 Intruder. Norman Friedman notes (“Postwar Naval Aviation” in Philip Jarrett (ed) ‘The Modern War Machine:
Military Aviation Since 1945′, London: Putnam Aeronautical Books, 2000) that the “Buccaneer [was] designed to fly Intruder-style all-weather low-level strikes. To a much greater degree than the Intruder it was intended to attack enemy warships; the RN had to concede most land attacks to the RAF.” The Buccaneer was effectively a sea-skimming fast jet that would have given Russian warships very little time to respond and would have posed a very difficult target for their air defence systems. In contrast, the Intruder and other US carrier aircraft were not optimised for anti-ship missions.
Rubel (p 23) reports the consequence. “In the late 1970s, as [US] naval aviation developed aircraft-centric aniship tactics … it became clear that a single strike on a single formation of Soviet ships might cost a quarter of an air wing.” While the US supercarriers were far superior to the ‘Ark Royal’ as strategic bombing platforms, the UK carrier looks to have been far superior as a naval warfare platform.
To repeat: carriers must be judged in relation to the missions they are intended to perform.
In conclusion, as Rubel (p 22ff) points out, there is room for a legitimate debate in the US regarding the future roles of the USN’s carriers. Should the strategic coventional bombing mission be abandoned? (As with the RN, this mission could be fulfilled by nuclear attack submarines with Tomahawk land attack missiles.)
Alas, this is not happening. Instead, there are shallow arguments over carrier vulnerability and whether the US should have carriers at all. Without carriers, the USN surface fleet could not operate outside the range of shore based air power, the US could not honour any of its alliance treaties, it could not defend its small island possessions west of Hawaii. The US would be forced into political isolationism. For Britain and France, carriers are essential for the defence of overseas territories, the independent support of allies, and the maritime defence of the home country.
For Brazil, China, India, Italy, Russia and Spain carriers provide important naval strategic options otherwise unobtainable. In all cases, the great benefit of a fast jet carrier is that it allows a surface fleet to manoeuvre freely on the high seas in time of crisis or war. All other surface fleets would be confined to a zone quite close – say, about 200 nm – from shore, because they would be dependent on shore-based air power, and so be relatively easy to find.