The 1st Marine Provisional Brigade, in conjunction with "Task Force Hill", mounted a massive offensive on Cloverleaf Hill and Obong-ni on August 17. At first tenacious KPA defense halted the Marines' push. The KPA then mounted a counterattack following this in hopes of pushing the Marines back, but this failed disastrously. By nightfall on August 18, the KPA 4th Division had been nearly annihilated and Obong-ni and Cloverleaf Hill had been retaken by US forces. The next day, the remains of the 4th Division withdrew completely across the river. In their hasty retreat, they left a large number of artillery pieces and equipment behind which the Americans used.