Balhae's aggressive expansion triggered frictions with Tang China, Silla of southern Korea, the Khitans, the Xi, the Göktürks, and several Mohe tribes.
732, King Mu ordered a punitive expedition against Tang in present-day Shandong, sending the Balhae navy at the command of Jang Mun-hyu.
In the same year, he led troops to Madushan (馬都山) in the vicinity of Shanhaiguan and occupied nearby towns.
In 727, Balhae began to dispatch embassies to Japan to avoid international isolation.
The king sent an official document to Japan indicating that Balhae recovered the terrain of Goguryeo and succeeded to the culture of Buyeo.