​​Roger Mengin, born in Paris in 1896, began his military career as a sub-lieutenant in the French Air Force. After joining the Free French Forces in London in 1942, he was promoted to the rank of commandant and served as a liaison officer with Allied forces. His role became critical during the final stages of the battle for Calais in September 1944.

​As Allied forces approached, around 24,000 civilians were still present in the city, which remained under German control. On 29 September, Mengin became the first French officer to enter Calais. Drawing on his previous experience in Le Havre and Boulogne, he proposed a civilian evacuation to avoid mass casualties. He negotiated directly with the German command, and a 24-hour truce was granted.

​To carry out the evacuation, Mengin travelled into the city alongside Hauptmann Böttcher in an open-top car. At Place Crèvecœur, he addressed the crowd from the steps of the Palais de Justice, formerly the town hall of Calais-Lès-Saint-Pierre. Welcomed by cries of “Vive de Gaulle! Vive la France!”, he urged the population to evacuate immediately, warning that the city faced destruction if the German garrison refused to surrender.

​His appeal succeeded. Within hours, La Marseillaise rose from the crowd, and a large-scale evacuation began under his coordination. By the time fighting resumed, approximately 20,000 civilians had been safely evacuated. Shortly after, the German commander, Oberst Schroëder, capitulated.

​Tragically, Mengin did not live to witness the full liberation. While travelling with Böttcher and Capitaine FFI Jacques Vendroux to report the surrender, their vehicle was hit by a misfired Canadian shell. Gravely wounded, Mengin was carried to a nearby bunker and then to Les Attaques, where he died in hospital, reportedly with the word “France” on his lips.

​Originally buried in Ardres, his remains were later transferred to Sainte-Geneviève-des-Bois (Loiret) in 1949. A commemorative plaque is located in the Palais de Justice, and a roadside stela marks the site of his final act of service.