This combination Cause_to_amalgamate proved fatal for the bases ' defenses , culminating Self_motion in a decisive French defeat Conquering at the Battle of Dien Bien Phu .

From then on , the French focused Aiming on creating Creating strong fortified positions , against which Viet Minh General Giáp could pit his forces , culminating in Operation Castor and the Battle of Dien Bien Phu .