The Siege of Calais was part of the broader German invasion of France during World War II. Facing intense pressure from advancing German forces starting in May 1940, the British Expeditionary Force and French troops were stationed in Calais to hold their ground and protect their flanks during the Dunkirk evacuation. Calais, due to its strategic positioning, became the focal point of an intense battle. Over the course of 13 days, the defenders faced relentless assaults and bombardments from Luftwaffe aircraft, greatly outnumbered by German tank and infantry divisions. On May 26, 1940, after enduring heavy casualties and dwindling supplies, the British and French garrison ultimately surrendered to the German forces.

The surrender of Calais was a devastating blow for the Allies, as it not only resulted in the loss of a key defensive position but also signified the reality of the German Blitzkrieg tactics that had been successfully implemented throughout the campaign. The fall of Calais allowed German forces to secure a wider front in northern France, complicating the Allied withdrawal from Dunkirk. The Allied troops at Dunkirk were only able to evacuate effectively because the Germans had diverted troops to complete the seizure of Calais rather than pursuing them relentlessly.

This event underscored the importance of morale and logistics in warfare, as many soldiers in Calais fought bravely despite knowing the limited chances of success. The siege was defined not only by the battle itself but also by the significance of the stalwart defense which provided critical time for other Allied forces to escape. The legacy of Calais would resonate throughout the war as it exemplified the determined nature of the Allied forces even in the face of overwhelming odds.