At places like La Bassée, the 1st Queen's Own Cameron Highlanders held out for two days, hurling back all German attempts to cross the canal. However, the cost was high; after one counter-attack, A Company had only six men left. On the morning of the 27th May, the defenders were finally overrun with the regiment being effectively wiped out. Only 79 members of the regiment made it back to England. That same morning at Festubert, the 2nd Dorsets were attacked by German panzers. However, clever use of the buildings in the town meant that they held out until nightfall before being ordered to retreat northwards to Estaires, some eight miles away. A fighting cross-country retreat to Estaires, which was being held by French troops, was successfully accomplished by day-break.

The 2nd Glosters and 4th Oxford and Bucks Light infantry turned the French town of Cassel into something resembling a fortress. They also had sufficient time to cleverly site and dig-in their anti-tank guns. This town, on a hill, had a commanding view of the Flanders plain and it was vital that it was held to buy time to establish defences around the Dunkirk beachhead itself. The town was surrounded and subjected to fierce and prolonged tank and infantry attack, but held out for three crucial days between the 27th and 29th May. Running low on food and ammunition, a breakout by the British troops was attempted on the night of the 29th May. However, few managed to evade the besieging German forces and the bulk of the force was captured and taken prisoner.

In the case of the defenders of the villages of Le Paradis (2nd Norfolks) and Wormhoudt (2nd Royal Warwicks), they had the misfortune to encounter SS troops of the SS Totenkopf and SS Liebstandarte. In each case, after surrendering, the survivors were shot by their captors, infuriated at the stiff resistance which they had encountered and their heavy losses.

On the 27th May, British and French Commanders met to establish a strategy for the defence of the Dunkirk beachhead itself. It was quickly agreed that the French would be responsible for the line west of Dunkirk and the British, everything east of the town. Referred to as the outer perimeter, it was 25miles long and approximately eight miles deep and it made the best use of the canal and waterways around Dunkirk to aid defence. In addition, low-lying areas such as Les Moeres on the eastern side of the perimeter were deliberately flooded to help impede the German advance. The French-held line ran from Mardyck – Spycker – Bergues. The British sector ran through the axis Bergues – Bulscamp – Furnes – Nieuport. The troops (British and French) allocated to provide the final rearguard must have realised, that in many cases, they were forfeiting their own chances of escape so that the greater part of the Allied armies could be saved. However, contemporary accounts record that the men involved accepted their fate stoically as they grimly set about establishing their defensive positions. As retreating units came into the perimeter, they were instructed to destroy vehicles and heavy equipment and in many cases, they were relieved of ammunition and automatic weapons by the rearguard soldiers to bolster the defender's armoury.

British units defending the perimeter included, among others, elements of the following regiments: the Loyals, Leicesters, Sherwood Foresters, Warwickshires, East Lancashires, Borders, Coldstream Guards, Duke of Wellington's, Green Howards, Durham Light Infantry, King's Own Scottish Borderers, Royal Ulster Rifles, Grenadier Guards, Berkshires, Suffolks, Bedfordshire and Herts, Duke of Cornwall's Light Infantry, East Surreys, Royal Fusiliers, South Lancashires and the Black Watch. From the 29th May, these units fiercely resisted strong attacks from German artillery and the several infantry divisions which had been assembled to take Dunkirk. Many of the books written over the past 70 years tend to dwell on two or three individual acts of heroism on the 'canal line' and the mens' respective units. It is however, perhaps, more fitting to remember the rearguard as a whole. The fact that each group of defenders was entirely dependent upon the units to its left and right holding their ground and that a major breakthrough at any point of the line would have brought the whole evacuation operation to a rapid halt. It was this team-work, resolve and self-sacrifice which was the real story of Dunkirk.

During the night of the 1st-2nd June, the survivors of the rearguard were withdrawn to an inner perimeter, utilising the Canal des Moeres and the Canal des Chats as its principal defence lines to the south and east. It was these defences which were taken over by elements of the French 8th Zouaves, 137th and 150th Infantry Regiments and the 92nd GRDI. This allowed the bulk of the British rearguard to be successfully evacuated on the night of the 2nd and 3rd of June.