Why were Royal Navy ships forbidden to attack the ARA Veinticinco de Mayo in Argentinian waters?

Q Why were Royal Navy ships forbidden to enter Argentinian waters?

Short answer:

Simply because the Royal Navy did not want to. Their own rules of engagement were laid out to limit the scope of this undeclared 'war' and avoid further escalation. Attacking an Argentine ship outside their flexibly defined zones of action was seen as leading to just that.
The explanation given in the video is misleading. If there is a war, then an enemy ship is fair game, no matter its position.

The quote from the video is just bogus. Part of a narrative seeking to explain something hard to explain by speculation. And using concepts for that that do not really apply.

The Splendid did not attack. Why? Just because they lost contact?

The question here is not "why". Instead it is the theoretical deliberation as to "would it have been allowed to attack?". And regardless whether this is answered yes or no: "which rules said so?"

First of all, an 'exclusion zone' is mainly for the benefit of other nations' vessels, mainly civilian vessels. If two parties are at war, then the warring party's vessels can be attacked by their counterpart even if outside that zone.

This is evidenced by the Belgrano attack, as the ship was outside that total exclusion zone and even Argentina admitted that to be "no breach of law" or simply: legitimate. Britain even made this intention public with a declaration that Argentine vessels were subject to attack if found outside that zone on 23 April, if posing a threat compliant, to art 51 UN charter…_{(Freedman: "The Official History of the Falklands Campaign. Vol. II", 2007, p 263.)}

But the interesting thing is then another bit of legalese the video ignores. "The Falklands War" was not a war! No war – no rules of war. The United Kingdom carefully avoided to declare war, and Argentina did not either. Argentina took the islands, Britain took them back. Some shooting occurred.

Declaring war is so outdated!

The whole operation was conducted under United Nations Charter Article 51, "Right to Self-Defence". That and in general public opinion of other nations made it necessary to try to confine the conflict as much as possible. An invasion of Argentina or really almost any kind of other escalation was unwanted. Therefore both sides predefined their rules of engagement.

What the video snippet might really refer to is 'forbidden under the rules of law as set up by the lawyers in the Foreign Office and the Royal Navy in their own Rules of Engagement!' In other words, that it was not an 'international law' but an internal order for British ships not to engage any ships, not even Argentinian outside that zone.

Timeline:

• 12 April –British declare Maritime Exclusion Zone MEZ
• 23 April – British announce in detail via Swiss embassy the clarification that any Argentine ship or aircraft that was considered to pose a threat to British forces, no matter what the position, would be attacked. In war a hostile naval vessel could be attacked at any location.
• 26 April – HMS Splendid loses contact with the ARA 25 de Mayo, which had a position north of the MEZ
• 30 April – an attack on the prime target ARA 25 de Mayo is authorised and ordered by Thatcher, but Splendid fails to locate it
• 1 May – armed hostilities begin
• 2 May – ARA Belgrano is sunk, Argentine carrier is ordered back to port, had jets with a range of 1000 miles on board but those needed favorable winds to take off and the ship itself developed boiler problems. British still want her sunk, too much of a threat
• 5 May – ARA 25 de Mayo is in shallow waters and Splendid nearby (src)

According to the twisted presentation of that documentary video, that is 'the point of return' for the HMS Splendid?

➔ Nothing from "the rules of war" prevented HMS Splendid from going after the carrier and attacking it! It's just that after the Belgrano was sunk it was deemed politically wise to not sink the carrier, even if deliberations went on that wanted her sunk in port!
For nothing more and nothing less than limit the conflict. And this close to thew coast it became just a bit difficult and dangerous to maneuver for the British boat.

If the video had stated that 'it was forbidden under current orders' or 'under then current British rules of engagement', then I wouldn't complain. But any 'exclusion zones, not even the just then made up 'total exclusion zone' has any relevance for exchange of shots under 'the rules of war'.

On May 7th, 1982, Argentina complained to the International Committee of the Red Cross in Geneva which ruled that the vessel, though outside the TEZ, was within the security zone of British ships in the area; was fully armed and engaged in operations and that therefore there was no breach of the Geneva Convention. The action was perfectly legal.

_{– Justin Kuntz: "“War Crime” allegations in the Falklands War Part Two: the sinking of ARA General Belgrano"}

These 'internal orders' or 'Rules of Engagement' (ROE) from the UK, for the UK forces, stand in marked contrast to those issued by Argentina for the Argentine forces. Both were not really compatible in any detail and illustrate perfectly that there was no 'outside rule' that unmistakably made any possible action HMS Splendid could have taken to be 'illegal'. Unwanted by the UK leadership, when taking into account international public opinion.

If all hinges on "poses a threat", then all you need is selling a sinking with the right spin. After all, the UK constantly emphasised that 'any additional measure' to its 'right to self-defense' was always still on the table…

Two sets of Rules of Engagement, set up ad hoc, may set a precedence for "the rules of war" in the future, but they do not retroactively make these rules pre-existing for these actions. Even establishing these kind of exclusion zones themselves, with their aggressive scopes and intentions, is a disputable practice.

Sinking a ship in the hot-zone of exclusion was seen as part of these twisted gentlemen agreements the ROEs were sold as. Attacking one slightly outside of it was feared as being seen as an escalation, more on a path to real war than whatever this was supposed to be.

Whether war in the North Atlantic during the Great War saw 'better' legal compliance from UK with blockading civilian shipping bound to Germany or German submarines attacking for example a military relevant Lusitania is still subject to interpretation. And since Argentina declared the entire South Atlantic as a war zone while the UK was similarly flexible in expanding the circles in which 'anything goes' was the goal, the lawyering about a fixed set of 'under the rules of war' seems quite misleading.

But these internal orders themselves are apparently still subject to different interpretations as to explain why the Splendid did not attack.

It is just this: if the Splendid would have been forbidden to do whatever "under the rules of war", then these posited 'rules of war' would have necessarily been applicable for both sides equally.

Sir John Nott has recently revealed the dilemmas facing the British government concerning the use of force in 1982:

The rules of engagement for our submarines posed rather different problems. As the submarines moved fast and submerged underwater, they only emerged infrequently to send and receive burst signals from satellite; so with two submarines fast approaching the Falklands, forethought was needed about what orders they should have when they encountered Argentine naval shipping or merchant vessels supplying the invasion force. It was this discussion which led to the recommendation for a maritime exclusion zone, which I announced in Parliament the following Wednesday.

One of the most vexing questions, extraordinary as it seems, was whether we could say that we were at war. Evidently not; we were strongly advised by the excellent Foreign Office lawyers not to declare war but to act entirely under Article 51 of the United Nations Charter, which gave the right to countries to act in their own self-defence.

The exclusion zones gave the nuclear-powered submarines carte blanche concerning the right to sink Argentine vessels around the Falklands.

The sheer complexity of operations facing the submarine commanders has been recently revealed in a first-hand account by another naval officer who records on 30 April that ‘Conqueror was trailing General Belgrano and Splendid had latched onto three frigates, hoping they would lead her to Veinticinco De Mayo. Spartan was still after the San Luis’. Other accounts about HMS Splendid’s patrol suggest that these ships were actually Argentine Type 42 destroyers (that in all likelihood would be escorts for Veinticinco De Mayo) and despite having them in his ‘sights’ the commanding officer of the SSN was not allowed under the existing rules of engagement to sink them. From this narrative, it seems that HMS Splendid trailed the warships for a period of time without sighting the aircraft carrier before being ordered elsewhere by Northwood.

_{— Alastair Finlan: "The Royal Navy in The Falklands Conflict ànd The Gulf War: Culture and Strategy", Frank Cass: London, Portland, 2004.}

And:

Redeployment of the SSNs did not immediately entail a revision of their ROE because reconnaissance did not require them to attack and their best form of defence, unlike the ships of the Carrier Group, was merely to avoid detection. But an ROE change was required if one of them was to be used against the 25 de Mayo outside the Exclusion Zone, from where the Argentine ship was capable of launching an air strike against the British Carrier Force operating within or on the periphery of the TEZ. According to Gavshon and Rice the Argentine aircraft carrier had been trailed by HMS Splendid until 23 April when, for reasons which remain obscure, this SSN had either been withdrawn from this task or simply lost contact' with the vessel. On 30 April Lewin persuaded the War Cabinet to authorise a further change in ROE and order HMS Splendid, which was patrolling north of the Exclusion Zone, to sink the 25 de Mayo if the carrier entered its patrol area. The Chief of Defence Staff insisted that this was a very precise and very limited ROE revision: 'I only requested approval for the carrier to be attacked.>32; 'it was not an order to the submarine "Go and sink the 25 de Mayo", it was an order to the submarine. If the 25 de Mayo finds you in the patrol area which you are in, you have approval to attack'.

As the Belgrano affair subsequently made clear, these extended Rules of Engagement were confined to HMS Splendid. HMS Conqueror was still operating under the original ROE which applied to the MEZ when she confirmed her detection of the Argentine cruiser group to the south of the TEZ on 1 May, and consequently her commander was not empowered to attack the Belgrano. Indeed he was specifically ordered not to do so unless the ship entered the TEZ.

_{— G. M. Dillon: "The Falklands, Politics and War", Palgrave Macmillan: London, 1989.}

See the different legal interpretations uttered over the course of this 'war' and how or whether any of that is covered in any legally binding way as analysed later:

The 1982 Falklands conflict once again brought attention to the use and meaning of naval exclusion zones. During the crisis both Great Britain and Argentina instituted several maritime zones. After Argentinean troops had landed on the Falklands on 2 April 1982 the British Government announced the establishment of a ‘Maritime Exclusion Zone’ (MEZ) that extended for 200 nautical miles from the centre of the islands. As from 12 April 1982 any Argentine warships and naval auxiliaries found within this zone were to be treated as hostile and were liable to be attacked by British forces.Neutral shipping and Argentine merchantmen and aircraft were not affected by this declaration. On 23 April 1982 Great Britain established a ‘defensive bubble’ around its Task Force, which was sailing to the islands. No specific limits were set for this zone. The warning was addressed to all Argentine warships and aircraft, including civil aircraft.

On 28 April 1982 the British Government introduced the ‘Total Exclusion Zone’ (TEZ) adopting the geographical limits of the previously established MEZ. As from 30 April the exclusion zone applied not only to Argentine warships and auxiliaries but also to merchant vessels and aircraft. Any vessel whether naval or merchant, and any aircraft whether military or civilian, ‘operating in support of the illegal occupation of the Falkland Islands by Argentine forces’ was to be regarded as hostile and consequently subject to attack without warning. In order to claim the status of ‘not hostile’ vessels required the authorization of the Ministry of Defence in London. On 7 May 1982 Great Britain took ‘additional measures in self-defence’ and issued a ‘new policy statement’ which read:

Because of the proximity of Argentine bases and the distances that hostile forces can cover undetected, particularly at night and in bad weather, Her Majesty’s Government warns that any Argentine warship or military aircraft which are found more than 12 nautical miles from the Argentine coast will be regarded as hostile and are liable to be dealt with accordingly.

Some observers, such as Barston and Birnie, refer to this measure as an extension of the TEZ of 28 April. It is worth mentioning, however, that this announcement only affected Argentine warships and military aircraft. Thus, using the term ‘extension’ is inaccurate. In the course of the conflict Prime Minister Thatcher stressed again and again that British measures were taken in self-defence under article 51 of the United Nations Charter. The same legal justification can be found in each letter of the British Permanent Representative to the United Nations to the President of the Security Council.

The different maritime zones were established ‘without prejudice to the right of the United Kingdom to take whatever additional measures may be needed in exercise of its inherent right of self-defence under Article 51 of the United Nations Charter’. During the conflict Argentina also declared three maritime zones. On 8 April 1982 the Argentine Government announced the establishment of a 200-mile zone around the Falkland and South Georgia Islands and off the Argentine coast. In this ‘theatre of operations’ military action could be taken if necessary in self-defence. As no vessel or aircraft was attempted to be excluded, this area can hardly be considered as an exclusion zone. In response to British measures of 28 April 1982 Argentina claimed the waters of the ‘Total Exclusion Zone’ to be Argentine territorial waters and announced that all British vessels, naval or commercial, and all British aircraft entering the zone would be liable to attack. Following the British policy statement of 7 May 1982, Buenos Aires declared on 11 May 1982, without further detail, that the entire South Atlantic was to be a ‘war zone’. Any British vessel found therein could be attacked on sight.

International reaction with regard to the establishment of exclusion zones was considerably muted. In fact, complaints were only made by Argentina and the Soviet Union. Moscow protested against the establishment of the British ‘Total Exclusion Zone’ effective as of 30 April 1982. The Soviets argued that British measures hampered free passage on the high seas, and, thus, violated the 1958 Geneva Convention on the High Seas and the 1982 United Nations Convention on the Laws of the Sea (‘UNCLOS’) respectively. Various legal experts, however, have rejected this argument by referring to article 2 of the Geneva Convention or article 87 UNCLOS. According to these provisions, exclusion zones appear not to be prohibited per se as ‘freedom of the high seas is exercised under conditions laid down in this Convention (UNCLOS) and by other rules of international law’ (emphasis added).

As far as the Falklands crisis is concerned, the doctrine agrees that since the Argentine invasion of the Falklands breached the duty of non-aggression contained in article 2(4) of the UN Charter, Britain could legally resort to defence measures. Under the UN Charter provisions, however, exercises of self-defence must be reasonable, limited to the necessity of protection and proportionate to the attack. Scholars tend to agree that the ‘Maritime Exclusion Zone’ was reasonable. As far as the ‘Total Exclusion Zone’ is concerned, the doctrine is divided. Some authors, such as Fenrick and Leiner, regard this zone as legitimate. The very absence of complaints of third states is a ‘strong indication that most interested states acquiesced in them as being reasonable and thus, lawful’. Others, such as Politakis, acknowledge Great Britain’s right to resort to force but question the proportionality and necessity of extending the ‘Maritime Exclusion Zone’ to the ‘Total Exclusion Zone’. Generally, Shearer questions the legality of the use of maritime exclusion zones in the Falklands conflict as they were primarily established to reclaim lost territory.

Taking into account world war and Falklands operations Zemanek observes that an international custom has been developed through ‘constant practice by all parties involved’ and advances two limitations for what he sees as a ‘new belligerent right’: first, the principle of necessity, and second, ‘belligerent duties towards neutrals’. However, he does not further define those ‘belligerent duties’. In addition, Zemanek supports the view that ‘the lawfulness of a war zone depends not on the declaring state’s ability to enforce it by effectively blocking entry through surface warships but rather on the probability of danger through continuous combat action which may also be created by submarines or mine fields’.

In contrast, for the late Professor Goldie, maritime exclusion zones enforced ‘sporadically or randomly merely by raiding tactics’ should not be seen as legitimate under customary law. As a consequence, indiscriminate sinking of merchant ships by submarines ‘as the main means of pursuing a raiding logistical strategy can not claim to fit under justifications which may uphold the legality of the persisting logistical strategies reflected in the Long Distance Blockades, respectively, the Entente Powers (in World War I) and the United Nations (in World War II)’.

Legal experts such as Fenrick, Fleck, von Heinegg, and Lyons agreed with van Hegelsom’s suggestions. Even though supporting the proposals in general, Shearer argued that as far as the legality of exclusion zones is concerned, a distinction should be made between defensive and offensive zones. Used defensively as a ‘trip-wire’ an exclusion zone might be legitimate ‘as the only practical means of discerning a hostile act’. If, however, used offensively (as in the Falklands crisis in order to reclaim lost territory) such a zone ‘may indicate only an intention to limit hostilities to a defined area’ and its legitimacy would remain questionable. According to Greenwood special attention should be drawn to the legal effects of the proclamation of an exclusion zone. He argues that the proclamation does not ‘significantly alter the rights of the belligerents and the neutrals within that zone’. Other participants strongly disagreed with van Hegelsom’s ‘Introductory Report’. These scholars regard exclusion zones as legally unacceptable in any circumstances.

_{— Christopher Michaelsen: "Maritime Exclusion Zones in Times of Armed Conflict at Sea: Legal Controversies Still Unresolved", Journal of Conflict & Security Law (2003), Vol. 8 No. 2, 363–390.}

British submarines had orders to stay away from these waters, at one time, then to ignore that and for a time they had explicit orders allowing an attack, if they find their target that is.

That changed as needed or requested and there just was no general prohibition throughout the war or even from before the start of it. The latter qualification one assumes is needed to comply with the phrase "… forbidden, under the rules of war, …".

It is remarkable that the video precedes the excerpt shown in question with '…and Splendid maneuvered for a shot…'. As the position of the ARA 25 de Mayo was always outside the relevant exclusion zone.

At the time this situation applied, Wikipedia states exactly this, coming from the very captain of that boat:

The captain of Splendid made the bold and disputable claim, that running on the edge of the exclusion zone around the Falklands, declared by the UK government, he had the right in international law and approval from the British PM, to fire at 25 de Mayo, a couple of miles away within Argentine waters, and would have fired MK 8 torpedoes at 25 de Mayo, if he had confirmed his precise position.

The taking of sides in great favor of one belligerent at the time seems a bit concerning here. If we take this one minute of Pym writing to the Prime Minister:

2. We have god reason to believe that she is in, or very close to Argentinian territorial waters, heading North and so away from the Falkland Islands and our task force, and that her attack capability is reduced to six aircraft with a radius of only 200 miles. Thus the carrier in her present posture can hardly be regarded as a direct or imminent threat to our task force.

• Pym as he wrote in the midst of the fog of war to the Prime Minister on 5 May 1982. https://c59574e9047e61130f13-3f71d0fe2b653c4f00f32175760e96e7.ssl.cf1.rackcdn.com/0627E18C1D4E476AB145BCF7182DAA5B.pdf

This means: they calculated the ship to be in that 'posture', without being sure. And "hardly" is still a matter of degree, dependent on correctness of data at the time and afterwards and interpretation, again for 'a while'. A heading can be changed, the number pf planes and capabilities greater than the estimate, and even a 'range of 200 miles' means that the islands are at the border and a good portion of the exclusion zone is well within their reach, as are all ships within the sector of overlap between range and MEZ. At that position depicted in the letter a change of course or a single simple launch of a plane could easily be taken as 'posing a threat', whether by a local commander or a London decision maker, or a spin doctor afterwards. These waters aren't the Gulf of Tonking, and the British sailors always honest Johns, but just taking a side in interpreting anything from a London government perspective – however fragmentary – in a maximally positive light is working on Maggie's farm still more.

And partly, that was the plan for the Argentinian side:

The commander of the theater of operations, Juan Lombardo , planned an operation for the Argentine fleet that he hoped would serve to distract the British fleet from its mission, which according to Argentine intelligence, was to support a landing in the Falklands that same day. The plan was to advance from the north to the Task Force aircraft -from 79.1 Veinticinco de Mayo - to the extent of the Exclusion Zone,

Regardless, emphasis on any 'rules' seems to ignore that these rules were not so much 'laws' but just rough guidelines to take into account outwards appearance more than anything else.

Remember that Splendid was already quite well outside the supposedly "zone of operations", strafing the territorial waters:

Splendid did not directly engage Argentinian forces, however she shadowed the Argentine aircraft carrier 25 de Mayo, with Splendid running within a mile outside of the Argentinian territorial line, 12 miles (19 km) off its Atlantic coast.

And the threat ARA the 25 de Mayo did pose a threat, while outside the exclusion zone:

In the absence of news of the carrier's position, Woodward ordered his planes to attempt a search. At 03.30 in the morning on 2 May, one of the Sea Harriers took off, piloted by Flight Lieutenant Ian Mortimer of the 801 Squadron on board the HMS Invincible, which, 200 miles to the northwest of the Task Force, had found with its radar what appeared to be the ARA 25 de Mayo and its escort vessels, rushing back to the carrier. Woodward then concluded, correctly, that the carrier group was planning an attack at dawn. In fact, the aircraft on the ARA 25 May were getting ready for a sunrise attack - although the mission was cancelled shortly afterwards and the ship and its escorts set sail for the mainland. But, this was only half the problem.

The ARA cruiser General Belgrano's group approaching from the southwest was the other half of the threat. The only option open to the British was to remove one of the arms of the pincer. The choice fell on the cruiser, quietly pursued by the submarine HMS Conqueror, commanded by Commander Chris Wreford-Brown. Wood-ward remarked: "I feel obliged to say that, if even the Spartan had been in contact with the 25 de Mayo, I would have recommended in the most emphatic way possible to attack both that night".

That same day, at an informal meeting in Chequers of most of the members of the OD (SA) (4), following a previous review of the situation by the Chiefs of Staff, the rules were changed to "allow attacks on any Argentine naval vessel on the high seas", as on April 30 had been agreed only for the ARA 25 de Mayo. The fate of the Belgrano was thus sealed.

"There was a clear military threat that we could not ignore without being irresponsible," Thatcher said. "It was one of the easiest decisions of the whole war", Nott said. The decision was made just two hours before the meeting between the Secretary Francis Pym and Alexander Haig, who would introduce him to the Peruvian peace process.

By the evening of May 2nd the threat was over. Fears about the effectiveness of nuclear submarines had materialized. The Argentine Sea Fleet retreated to shallow waters, without being presented with another favourable opportunity for a new decisive attack in the rest of the conflict. The ARA 25 de Mayo, with propulsion problems, was left in shallow waters, but not before landing its air component to continue the fight from land bases.

• ALEJANDRO J. AMENDOLARA: ¡HUNDAN EL PORTAAVIONES!, Boletín del Centro Naval, Número 817 Mayo/agosto de 2007. https://www.centronaval.org.ar/boletin/BCN817/817amendolara.pdf

And as evidenced here, the General Belgrano was simply 'declared to be a threat.'

The 'official history' by Sir Freedman paints a rather different light but also for a larger picture:

London was reluctant to begin all-out submarine warfare, but with Pym having now left Washington without any diplomatic breakthrough in sight, and evidence of an Argentine readiness to attack British vessels, Nott instructed the SSN Splendid, then in the Falklands MEZ, to proceed in the direction of the area in which the main Argentine force was patrolling. This would create the option of being able to execute retaliation should ministers so decide following an attack upon a British ship in the South Georgia area. This indicates that politically the critical consideration was where, when and against whom the first shots were to be fired rather than the second shots.

After the War Cabinet meeting that day Lewin told the Prime Minister that ‘it had been possible to identify the location of the Argentine naval force including the aircraft carrier 25 de Mayo in a patrol area between the Argentine coast and the Falkland Islands Maritime Exclusion Zone,’ and that he had ordered Splendid, which was some two days’ sailing away from this area, to conduct surveillance operations in the carrier’s likely vicinity and prepare for offensive operations against the group if so ordered. For the moment existing ROEs would be in effect: SSNs could not attack surface ships except in selfdefence but could attack any conventional submarine detected. When the Foreign Secretary found out about this he was extremely concerned, not least because he had been left the impression at the War Cabinet meeting that day that no decisions had been taken on SSN operations outside the MEZ. There was a risk of a major incident once they began and he was just about to leave for sensitive negotiations in Washington.

Nonetheless, as a result of the FCO position, the orders to Splendid were reversed. As an attack on the carrier would not be ordered in these circumstances there seemed to be little point in using up an SSN just on surveillance. Nevertheless, on 24 April further intelligence, and the imminent arrival of the Task Group into the Falklands area, led to the orders to Splendid to conduct surveillance and prepare for offensive operations against the carrier group being reinstated. By the next day there was intelligence that the 25 de Mayo and the Santisima Trinidad had left Puerto Belgrano and moved south. The problem was now finding the group with sufficient accuracy to permit an attack and a day later Splendid was still being instructed to do so.

The need to prepare specifically for an attack on the carrier was raised at Chequers the next day. There was considerable apprehension among ministers. All agreed that it was essential to protect the amphibious force at the moment of greatest danger, that the essential first step was to close down Stanley airport to all Argentine aircraft capable of interfering with a landing, and that dealing with the 25 de Mayo might well be a sensible second step. Otherwise, as the First Sea Lord warned them, the British air defences might become just too stretched. If the Argentine Air Force was also close to the limits of its range over West Falkland, then the carrier provided Argentina’s most likely means of mounting a serious threat to the Task Force. Yet sinking the carrier seemed a large step to take. Nott worried about a ‘horrible logic’ that would see the taking out of Argentine airfields as the move after that. Whitelaw wondered whether public opinion was ready for the sinking of a carrier. Thatcher took the view that it would find that more acceptable than attacks on their airfield, which might be understood as putting civilians at risk. Leach followed this by insisting that taking out the carrier was essential to the future security of the Falkland Islands and then Lewin came in arguing that it was essential for the security of the amphibious force, so much so that it needed to be taken out by 3 May. Then there was the question of whether a warning should be issued to the Argentines to stay clear of the zone of operations, but against this came the objection that this would merely encourage the Argentine Navy to hold the carrier close to the mainland until its aircraft were most needed. Given the uncertainties surrounding the Haig negotiations at the time, and in the light of South Georgia, a warning could appear provocative. Not issuing a warning and then sinking the carrier would be even more provocative. The decision was too momentous for the War Cabinet to take at that time. Ministers agreed that Nott should be invited to report further on the appropriate ROE if it did become necessary to attack the carrier outside the Exclusion Zone and on the possibility of issuing a warning.

It was recognised that this issue would raise all the difficult questions of military escalation. The military logic was pointing to taking every possible action to reduce the threat to the Task Force. For example, if, as was at times claimed, the operating distance of aircraft launched from the carrier was as much as 500nm, this was significantly greater than the distance between the Argentine mainland and the Falklands. This could lead to a case for attacking the carrier in port, where at least casualties could be kept down, and this could lead by extension into a case for attacking mainland bases. Yet the political logic stressed the need to avoid escalatory or provocative action, especially while negotiations were still underway, and to stay within the framework of international law. The FCO’s Legal Adviser was clear that the carrier could be sunk on the high seas as soon as its aircraft were in range of the Task Force, especially if a clear warning had been given that if it moved beyond a certain point the carrier could expect to be attacked. Attacking without warning would be much more problematic. It would be appropriate to inform Argentina, through the Swiss, that if the carrier moved south or east over a designated boundary line this would be considered a hostile act.

The Chiefs of Staff, taking their cue from the Chequers meeting, began to review the carrier issue on 26 April. The First Sea Lord made the running. Once the 25 de Mayo could sail with Super Etendards he argued, it would be hard for the Task Force to anticipate when an attack would materialise. He therefore judged it essential for the safety of Britain’s own ships that preemptive action be taken as soon as an attack was threatened. It would not be safe to wait under such circumstances for decisions to be taken in London and then transmitted to the SSNs. He set a deadline for 3 May on how to deal with the carrier including the extent to which Argentina should be made aware of what had been decided. The Chief of the General Staff rejected the possibility of an attack without warning before a hostile act had been committed or the Task Force approached. The FCO representative also warned of legal problems if a presumed hostile intent was declared at ranges as great as 500nm. The Navy were unconvinced: at the carrier’s operating range even declaring a zone out of which the carrier should not move could define a sanctuary from which it could present a constant threat. The inconclusive debate led to Lewin proposing the drafting of a paper for the next day addressing the nature, range and timing of the threat posed by the aircraft carrier; the options available to the Task Force Commander to protect the Amphibious Force; the means of reducing the threat either by authorising pre-emptive attacks or by declaring special zones; the advantages and disadvantages of giving a warning of Britain’s intentions; and action to be taken in respect of survivors of any attack.

The same day, the Task Force commanders decided to approach the issue from another angle. The starting point was an anomalous situation that had arisen with regard to one of the critical rules of engagement, rule 206, according to which authority would be delegated to assume that an attack by an enemy unit was the first in a set of pre-planned multiple attacks. In such circumstances the British would wish to strike all threatening units to reduce the further risk to ships of the Task Force. What might constitute a ‘threatening unit’ would vary but in almost all circumstances would include the carrier. This rule, however, only applied to RN aircraft or surface ships: the ROE for SSNs only permitted attacks outside the TEZ in self-defence or against a detected conventional submarine. Northwood therefore proposed that a new rule should be devised to cover a contingency, in which a multiple attack could be about to occur and an SSN was trailing the carrier. If Woodward then determined that the carrier was a threatening unit, Northwood would authorise an attack. Against the claim that the critical issue here was conformity between the SSNs and aircraft and surface ships, Sir Ian Sinclair, the FCO Legal Adviser, was dubious that this issue was really different from the general issue of when to attack the carrier.

Now that it had some contacts Splendid was reluctant to move again, but there was still no sign of the carrier, though from the next morning it knew of the change in ROE allowing for an attack on the 25 de Mayo. Splendid now had a position where it expected the 25 de Mayo to rendezvous with its escorts, but when it arrived at 0800Z on 1 May, it found nothing. Several sonar contacts were made, including possibly some warships, but none that indicated the presence of an aircraft carrier. It went to periscope depth but failed to make a sighting and by 0900Z concluded that there were no contacts in its chosen area. It searched for some time and then went north on another fruitless journey to investigate possible signs of an Argentine submarine.

• Sir Lawrence Freedman: Official History of the Falklands Campaign. Volume II: War And Diplomacy, Routledge, 2005.

If we align the timeline as presented in the video, the Pym letter is indeed irrelevant, as by then the possible action alluded to and reasoned for here on this thread was days in the past. As military logic often goes, the mere existence of such an armed vessel is a thread, pre-emptive strikes not uncommon, communication with the submarine hampered, and at the relevant time in favour of an attack. And thus the events as unfolded were not governed by any rule preventing action, but in fact more a result of contingency. In other words luck for the ARA 25 de Mayo.