 PAVN, which had been operating a more conventional, large-unit war, switched back to small-unit operations in the face of U.S. military capabilities.The struggle moved to the villages, where the "hearts and minds" of the South Vietnamese peasants, whose cooperation was absolutely necessary to military success, would be won or lost.The U.S. had given responsibility for this struggle to the Army of the Republic of Vietnam (ARVN), whose troops and commanders were notoriously unfit for the task.