A summary of the WWII events this day:

• French PM Reynaud appeared before his parliament and blamed the military disaster on incredible faults in the French high command that he said would be punished.
• Churchill’s 1st meeting with new Allied Commander General Weygand.
• BEF evacuations from French coast, planned at 10,000 per day from 3 ports.

From Walter Lord’s book, The Miracle of Dunkirk, the evolution of evacuation planning:

On May 19 General Riddell-Webster presided over a meeting at the War Office, taking up for the first time the possibility of evacuation. There was no feeling of urgency, and a representative from the Ministry of Shipping felt that there was plenty of time to round up any vessels that might be needed.

Calais, Boulogne, and Dunkirk would all be used, the meeting decided. The basic plan had three phases: starting on the 20th, “useless mouths” would be shipped home at a rate of 2,000 a day; next, beginning on the 22nd, some 15,000 base personnel would leave; finally, there was just possibly “the hazardous evacuation of very large forces,” but this was considered so unlikely that the conferees did not waste their time on it.

Next day, the 20th, when Ramsay called a new meeting at Dover, events had changed everything. The panzers were pointing for the coast … the BEF was almost trapped … Gort himself was talking evacuation. “The hazardous evacuation of very large forces” no longer sat at the bottom of the agenda; now “the emergency evacuation across the Channel of very large forces” stood at the top.

The situation was still worse when the same group met on the 21st, this time in London again. Another plan was hammered out; more neat, precise figures. Ten thousand men would be lifted every 24 hours from each of the three ports—still Boulogne, Calais, and Dunkirk.

From Walter Lord’s book, The Miracle of Dunkirk; After British Army Chief Edmund Ironside got BEF Commander Gort to agree to attempt to attack going south, instead of retreating north [Dunkirk], the following happened:

At 2:00 p.m., May 21, a scratch force under Major-General H. E. Franklyn began moving south from Arras. If all went well, he should meet the French troops heading north in a couple of days at Cambrai. But all didn’t go well. Most of the infantry that Franklyn had on paper were tied up elsewhere. Instead of two divisions [10,000 soldiers per division] he had only two battalions [845 soldiers per battalion]. His 76 tanks were worn out and began to break down. The French support on his left was a day late. The new French armies supposedly moving up from the Somme never materialized. The Germans were tougher than expected. By the end of the day Franklyn’s attack had petered out.

This was no surprise to General Gort. He had never had any faith in a drive south. Midafternoon, even before Franklyn ran into trouble, Gort was giving his corps commanders a gloomy picture of the overall situation. Franklyn’s attack was brushed off as “a desperate remedy in an attempt to put heart in the French.”

Meanwhile, at another meeting of staff officers, Gort’s Adjutant-General, ordered rear Headquarters to move from Boulogne to Dunkirk; medical personnel, transport troops, construction battalions, and other “useless mouths” were to head there at once. Later, at still another meeting, a set of neat, precise instructions was issued for the evacuation of these troops: “As vehicles arrive at various evacuation ports, drivers and lorries must be kept, and local transport staffs will have to make arrangements for parking. …”

[Gort’s Chief of Staff] Pownall summoned the acting Operations Officer, Lieutenant-Colonel Bridgeman. The purpose, it turned out, was not working on the drive south. Rather, he was to draw up a plan for retiring north … for withdrawing the whole BEF to the coast for evacuation.

Bridgeman worked on it all night. Starting with the premise that an evacuation could take place anywhere between Calais and Ostend, he had to find the stretch of coast that could most easily be reached and defended by the three corps that made up the BEF. Which had the best roads leading to it? Which had the best port facilities? Which offered the best chance for air cover? Which had the best terrain for defense? Were there canals that could be used to protect the flanks? Towns that could serve as strong-points? Dykes that could be opened to flood the land and stop those German tanks?

This same morning Winston Churchill again flew to Paris, hoping to get a clearer picture of the military situation. Reynaud met him at the airport and whisked him to Grand Quartier Général at Vincennes, where the oriental rugs and Moroccan sentries lent an air of unreality that reminded Churchill’s military adviser, General Sir Hastings Ismay, of a scene from Beau Geste.

Here the Prime Minister met for the first time Maxime Weygand. Like everyone else, Churchill was impressed by the new commander’s energy and bounce (like an India rubber ball, Ismay decided). Best of all, his military thinking seemed to parallel Churchill’s own. As he understood it, the Weygand Plan in its latest refinement called for eight divisions from the BEF and the French First Army, with the Belgian cavalry on the right, to strike southwest the very next day. This force would “join hands” with the new French army group driving north from Amiens. That evening [21st] Churchill wired Gort his enthusiastic approval.