After the armistice of 1940, "Imprimies Reunites" was a centre of the French Resistance in Rennes, printing and distributing underground papers as part of "Libération Nord", including "Libération", "le Patriote", "la Flamme" and "le Populaire" (the latter had been a daily until the German invasion but was printed clandestinely from 1942). Commeurec was the leader of the socialist party in Rennes. From 1941, he made false documents for escaped soldiers with the typographer Marcel Besnard, from models by Gache and Dehalay. In August 1943, he became liaison officer for the "Bordeaux-Loupiac" network having been recruited by André Heurtier. He was chairman of the departmental Clandestine Liberation Committee and retrieved weapons parachuted in by the British. On 8 February 1944 he was arrested by the Gestapo and tortured at . On 29 June, he was transferred to Fronstalag-122 internment camp at Royallieu-Compiègne and then taken from France with 147 others to the Neuengamme concentration camp network centred in south-eastern Hamburg on Transport No. 415. He was given the registration number 40160. On 13 February 1945, he died of exhaustion aged 66 at Stalag X-B, a satellite camp of Neuengamme at Sandbostel, where prisoners suffering from epidemics were often taken. His body was repatriated and reinterred in 1946 at the "" in Rennes.