In 185 BC, Empress Lü's officials outlawed trade of iron and horses with Nanyue. Zhao Tuo retaliated by proclaiming himself Emperor Wu of Nanyue and attacking the neighboring kingdom of Changsha, taking a few border towns. In 181 BC, Zhou Zao was dispatched by Empress Lü to attack Nanyue, but the heat and dampness caused many of his officers and men to fall ill, and he failed to make it across the mountains into enemy territory. Zhao began to menace the neighboring kingdoms of Minyue, Xiou (Western Ou), and Luoluo. After securing their submission he began passing out edicts in a similar manner to the Han emperor.