Generally speaking, Nanzhao was then the most powerful kingdom in mainland Southeast Asia, and played an extremely active role in multistate interactions. In 859, Nanzhao captured Bozhou, and this event exacerbated the Nanzhao-Tang clashes. When the Tang governor of Annam took Bozhou back in the following year, Nanzhao, with the help of native peoples, occupied Hanoi as the Tang army moved to Bozhou.