Operation Catapult is a highly interesting chapter of WW2 yet at the same time one that is somewhat neglected in historical discourse and even more so in public discourse which may be partly due to diplomatic concerns which might fade away now 65 years after the end of WW2. When thinking of WW2 we just don't tend to think of English shooting at French.
As for the question "was it necessary" which has been put up here we mustn't forget that we are benefiting from the benefit of hindsight which the British at the time didn't have. We must see the attack in the context of 3rd July 1940 and from the British point of view that context really sucked as demonstrated for example in Winston Churchhill's speech
We shall fight on the beaches which was held on June 4th under the impression of the evacuation of Dunkirk but several weeks before the ultimate surrender of France on June 22nd. The speech is of course one to encourage people, but it clearly addresses the risk of German invasion the British isles and the outcome of the impending Battle of Britain was uncertain at the time.
The British still had a far superior traditional navy compared to the German navy which was heavily based on submarines. There was a great fear from the British side of the Germans taking over the French fleet which combined with the existing German fleet might have proved a much more serious thread to the Royal navy than the German fleet (two modern battleships) by itself did.
The impending replacement of big battleships by aircraft carriers was not yet foreseeable for everyone. In fact the British had already lost the carrier
HMS Courageous to a German submarine as early as September 1939, and the carrier
HMS Glorious to the guns of the battle-cruisers Scharnhorst and Gneisenau on the 8th of June 1940 (another piece of ill news that was still very fresh in the British consciousness) while the great successes of the aircraft carriers (who had so far sunk nothing bigger than the light cruiser
Kˆnigsberg which had previously been damaged by coastal artillery) were yet a matter of the future. The first great success of aircraft carriers in WW2 was be the
attack on Tarento in November 1940 against the navy of Italy who had joined the war on June 10th 1940 (yet another piece of bad news to England in these harsh summer of 1940 as Italy's declaration of war meant that the Mediterranean and North Africa were to become a theater of the war. In this context it is interesting to note that the British planes during operation Catapult were used only to mine the harbor entrance rather than directly attacking the French ships (but six British planes shot down by French ones were the only British casualties in the operation). Another point to notice (I feel I am getting a bit off topic) is that a few days after the attack on Mers-el-KÈbir planes from the Ark Royal attacked the already damaged battleship Dunkerque and further damaged it without sinking it however (point being that at this time of the war aircraft carriers and their planes did not come across as the nemesis to battleships as they did at a later time in the war).
British fear of Germany obtaining a navy that would enable them to blockade the British Isles (as they later tried to do with submarines only) was very high at the time. We are not talking of a matter of mere national pride (Britania rules the waves) either. It is often overlooked that the British blockade against Germany in WW1 caused the death of at least 750 000 civilians by starvation and there was great fear on both sides in WW2 to be subjected to as active a blockade (which did not work out as much in WW2, it wasn't until the final year of the war that food was running out in Germany which however was largely due to the ruthless robbing of conquered country's food resources).
The British at the time couldn't be certain if the French fleet wouldn't end up in German hands after all (in a time when French WW1 hero
Phillippe PÈtain showed readiness to collaborate with the Germany everything seemed possible). With the high stake for the British and the uncertainty about what the French were going to do the British couldn't without great risk accept the French refusal of their ultimatum to ensure the French fleet was not going to fall into German hands by one of the following options:
(a) Sail with us and continue the fight until victory against the Germans.
(b) Sail with reduced crews under our control to a British port. The reduced crews would be repatriated at the earliest moment.
If either of these courses is adopted by you we will restore your ships to France at the conclusion of the war or pay full compensation if they are damaged meanwhile.
© Alternatively if you feel bound to stipulate that your ships should not be used against the Germans unless they break the Armistice, then sail them with us with reduced crews to some French port in the West Indies ó Martinique for instance ó where they can be demilitarised to our satisfaction, or perhaps be entrusted to the United States and remain safe until the end of the war, the crews being repatriated.
If you refuse these fair offers, I must with profound regret, require you to sink your ships within 6 hours.
Finally, failing the above, I have the orders from His Majesty's Government to use whatever force may be necessary to prevent your ships from falling into German hands.
The anger of the defeated French seemed a lesser price to pay for the British than the looming risk of a united French, German, and Italian fleet. The decision to attack was cruel but consequent and from the British point of view necessary at the time.
The
Scuttling of the French fleet in Toulong in November 1942 sort of redeemed the French and can be held up as a point that they would not have permitted their fleet to be taken over by the Germans in the summer of 1940 either. However, the argument is not unimpeachable. There is a chance that Operation Catapult may have played a role in the lack of German attempts to get hold of that fleet in the summer of 1940. Shocked by their defeat and with the apparently impending victory of the Germans the French might (I am not saying they would have, but it is a possibility) been less determined to rather destroy their fleet than let it fall in German hands than they were in November 1942 when the situation began to look much less favorable to the Germans. We must always keep the circumstances of a given point in time in mind when "judging" (not a good term here) historical events.
Finally I wold like to point out that the attack on Mers-el-KÈbir was by no means a precedent. In April 1801 the Royal Navy destroyed much of the Danish-Norwegian fleet in the
attack on Copenhagen. The cases are not really the same as Great Britain and Denmark had not been allies before and Denmark had not been conquered by Napoleon Bonaparte. However, Denmark (which had a very strong navy at the time) had joined a league of armed neutrality which the British felt to serve French interest. There was great fear that the Danish fleet would team up with the French (same as the fleet of Spain) so the British attacked. Same as with Mers-el-KÈbir the British sent an ultimatum (to leave the league of armed neutrality) before attacking the navy of a country that they were not at war with at the time.