At the start of July 1944, Guingouin had been warned that a German offensive was being prepared against his maquis. On the 17th, the 1st brigade was attacked by the German brigade of General Curt von Jesser with a strength of 500 vehicles, supported by various reinforcements. This triggered the battle of Mont Gargan. The maquis lost 97 men (38 dead, 5 missing, 54 wounded) against 342 killed and wounded on the German side. It was one of the rare occasions when the resistance fought against the Wehrmacht in open battle.