In 1608, Kikkawa Hiroie built Iwakuni Castle atop Mt. Yokoyama overlooking the Nishiki River. At Sekigahara in 1600 he had secretly negotiated with the Tokugawa while positioned on Mt. Nangu with the Western Army, blocking the main Mori force from joining the battle. Afterward, amid the Mori's reduction, he was granted Iwakuni (30,000 koku) and became its first lord.