The Battle of Britain Five Months That Changed History, May—October 1940 by James Holland (z-lib.org).epub

Trouble at Sea: Part 1
‘TOMORROW AT DAWN, we put into operation a plan called CATAPULT,’
jotted Jock Colville on 2 July, ‘which entails the seizure of all French ships
in British ports, and, later in the day, an ultimatum to the big French capital
ships at Oran.’ Concern about the French Fleet had been mounting in
London. The Kriegsmarine on its own might not have been a match for the
Royal Navy; the German and the Italian fleets together made a formidable
enemy; but the German, Italian and French fleets could prove potentially
disastrous. By the original terms of the armistice, the French Fleet was to
assemble at French ports under German and Italian control, but Admiral
Darlan, the French C-in-C, decided to send the bulk of the Fleet to its base
at Mers-el-Kébir, near Oran, in French Algeria. The Germans did not object
to this.
The British did, however. Both the British and Général de Gaulle made
a plea for all French ships and forces to continue to fight and, in the case of
the French navy, head for British ports. Some did, including two old
battleships, several destroyers and a number of submarines. There were also
several capital ships at Alexandria. These refused to join the British, so
were immediately demobilized under British instructions.
Both Darlan and Marshal Pétain insisted that no warship would be
allowed to fall into German or Italian hands, but however honourable may
have been their intentions, Vichy France was now a German vassal state
and their ability to enforce such a declaration was limited to say the least.
From the British perspective, the risk of those ships being turned over to the
enemy was simply too great. On 28 June, the Cabinet came to a difficult,
but unanimous conclusion. The French Fleet at Oran and Algiers must
surrender to the British or be attacked and destroyed. ‘This was a hateful
decision,’ noted Churchill, ‘the most unnatural and painful in which I have
ever been concerned.’
The man given the job of confronting the French Fleet was Admiral
James Somerville, now commander of the powerful Force H, hastily sent to
guard the Western Mediterranean in the absence of the French. Somerville,
like many in the Royal Navy, knew a number of his French counterparts