He fought in the 1940 Battle of the Somme (generally identified in English-language sources as the Battle of Abbeville) between 27 May and 4 June 1940, and then in a succession of smaller "delaying actions", first alongside the Seine where the Germans were fighting to capture a series of critical bridges before defenders could blow them up, and then further to the west in Normandy and Brittany. The German invasion of France is nevertheless remembered for the speed with which German forces were able to use their air superiority and pioneer new motorised warfare techniques to capture the northern part of the country. German armies entered Paris on 14 June 1940 and the French government signed an armistice a few days later. By 16 June 1940 Claude Hettier de Boislambert was at the port of Brest. As France fell, he resolved to continue the fight, which meant crossing to Britain, which he did accompanied by those officers and sub-officers who had been fighting under his command who now volunteered to follow him. They travelled on a liner/troop ship that the English had sent to pick up Polish troops who had been fighting in France against the German invasion, having fled the German-Soviet occupation of their own country.