The Viet Minh launched a massed assault against the exhausted defenders on the night of 1 May, overrunning "Eliane" 1, "Dominique" 3, and "Huguette" 5, although the French managed to beat back attacks on "Eliane" 2. On 6 May, the Viet Minh launched another massed attack against "Eliane" 2, using, for the first time, Katyusha rockets. The French artillery fired a "TOT" (time on target) mission, so that artillery rounds fired from different positions would strike on target at the same time. This barrage defeated the first assault wave, but later that night the Viet Minh detonated a mine under "Eliane" 2, with devastating effect. The Viet Minh attacked again, and within a few hours the defenders were overrun.