 Langlais arrived in Indochina as a Battalion Commander in the 9th Colonial Infantry Division (9e DIC) in October 1945.His battalion participated in the early battles of the First Indochina War, including the Battle of Hanoi in December 1946.Langlais distinguished himself as a promising young battalion commander in the bitter house-to-house fighting prevalent throughout this battle, which eventually resulted in the French reoccupation of Hanoi.