[citation needed] Following the outbreak of the Second World War, Nicholson was given command of the 30th Infantry Brigade, which was raised on 20 April 1940 to serve in Norway.
As the large German force fought through the town the same day, Nicholson ordered a staged withdrawal from the ramparts to more easily defensible places in the city, such as the Citadel and the Gare Maritime, a train station.
Soon after, Nicholson received a telegram from Anthony Eden, Secretary of War: "Defence of Calais is of vital importance to our country and BEF and as showing our continued co-operation with France.
The eyes of the whole Empire are upon the defence of Calais, and His Majesty’s government is confident that you and your gallant regiments will perform an exploit worthy of the British name."
He spurned the offer, and four days of intense street fighting passed before silence reigned over Calais, which marked the end of a memorable resistance.
They have added another page to the glories of the Light Division and the time gained enabled the Gravelines Walnlieu to be flooded and to be held by French troops; and thus it was that the port of Dunkirk was kept open.
[3] While imprisoned, Nicholson was asked to be an independent witness that the Germans did not perpetrate the Katyn massacre, where around 20,000 Polish officers and intelligentsia were killed by the Soviets.
In 1966, Lionel Ellis, the British official historian, wrote that three panzer divisions had been diverted by the defence of Boulogne and Calais, giving the Allies time to rush troops to close a gap west of Dunkirk.
In 2006, Karl-Heinz Frieser wrote that the halt order issued to the German unit commanders because of the Anglo-French attack at the Battle of Arras (21 May) had a greater effect than the siege.
Hitler and the higher German commanders panicked because of their fears of flank attacks, when the real danger was of the Allies retreating to the coast before they could be cut off.
In the film, Churchill orders Nicholson to hold out and delay the Germans so that the bulk of the British Expeditionary Force can be evacuated from Dunkirk.