On 22 May, elements of the 20th Guards Brigade arrived at Boulogne from training camps in Surrey, just in time to defend against the huge firepower of the 2nd Panzer Division until the following evening, when the order was given to evacuate all troops onto Royal Navy warships. Around 300 Welsh Guards remained, holding out for another 36 hours until they ran out of ammunition and surrendered.
That same day, 23 May, Calais was attacked by the 1st and 10th Panzer divisions. Handicapped by contradictory orders and facing massively superior forces, the British troops nevertheless succeeded in holding off the German advance.
By the next day, British troops in Calais had been joined by some French and Belgian volunteers. Although supported by the Navy and RAF, they remained hopelessly outnumbered and outgunned. Both sides sustained heavy casualties and by the night of 26 May, Brigadier Nicholson, Commander of the Calais Garrison, was running out of men.
The Germans advanced through Calais, slowly taking the Allied strongholds and capturing the few remaining men. However, the four-day defence of Calais had helped to give the Allies essential time to start their evacuation from Dunkirk