During September 1950, Segrétain alerted command of the three strong positions of artillery while his men picked up their traces at the frontier. The 1er BEP received for mission to retake the town of Dong Kje on colonial route 4 (RC4) while assuring liaison with That Khe situated at 20 km south. While facing a superior enemy in numbers, the 1er BEP would have to make movement towards the cuvette of Coc Xa; surrounded by rocks and vegetation, the 1er BEP (I formation) delivered the first traditional Foreign Legion battlefield of the First Indochina War throughout which the entire battalion was annihilated. Battalion commander "Chef de bataillon" Segrétain commanded his unit till his last effort. Pierre died of his mortal wounds during the night of 7–8 October 1950, while the remaining survivors of the battalion were filtering across enemy lines to win back That Khe.