In McCarten’s book I see no explanation as to what changed Churchill’s mind and strengthened his resolve from May 26, 1940 to May 27, 1940, which culminated with Churchill winning over the extended cabinet of 25 MPs on May 28 at his office at the House of Commons at 6:30 pm.
There is also no mention in McCarten’s book of two important facts. First, on May 24 at 11:42 a.m., Hitler issued the halt order, sent in clear, and instantly read in London, which stopped the advance towards Dunkirk and did not rescind it until late May 26, so on May 26, at 5 p.m. when the crucial meeting took place, Churchill already knew that there was a chance to use this pause to help evacuate the troops and indeed the order to initiate operation Dynamo was given a few hours after the fall of Calais the same day, whereas by May 27 the German tanks had continued their advance. So why would Churchill have been more resolute on May 27 than on May 26?
Second, the chiefs of staff came up with a paper on May 25 entitled “British Strategy in a Certain Eventuality “, which [from Lukacs’s Five Days in London, May 1940, page 107] ‘presumed the worst possible conditions - and, by 25 May, and increasingly plausible situation: the French making peace with Germany, Italy entering the war, Europe and French North Africa under German control and the loss of most of the British Expeditionary Force still struggling in northern France and Belgium . Still – even in these conditions Britain could hold out, if the United States would support Britain increasingly, eventually entering the war, and if the Royal Air Force, together with the navy, would remain in control over Britain and thus “prevent Germany from carrying out a serious seaborne invasion “’.
I personally believe that one of the main reasons Churchill did not give in is that in contrast to all the political class of the day (and almost all of the political elites of today), he knew whom he was dealing with. He knew what his enemy believed in. He had read Hitler’s Mein Kampf – “ the new Koran of faith and war”. [from The Gathering Storm, VOL 1 of The Second World War, page 26]. He knew what to expect from Hitler.