On 15 March, the Soviets dispatched another 30 soldiers and six combat vehicles to Zhenbao Island. After an hour of fighting, the Chinese had destroyed two of the Soviet vehicles. A few hours later, the Soviets sent a second wave with artillery support. The Chinese destroyed five more Soviet combat vehicles. A third wave was repulsed by effective Chinese artillery, which destroyed one Soviet tank and four APCs and damaged two other APCs. By the end of the day, with the Chinese in full control of the island, Soviet General OA Losik ordered to deploy then-secret BM-21 "Grad" multiple rocket launchers. The Soviets fired 10,000 artillery rounds in a nine-hour engagement with the Chinese along with 36 sorties.