Veteran Nguyễn Hữu Chấp, former commander of a sub-division of Division 312, the unit in charge of opening fire to launch the Điện Biên Phủ campaign, said the Him Lam Base was guarded by the 13th Foreign Legion Demi-Brigade, one of the most famous, battle-hardened units of the French Legion, considered "invincible" in World War II.