and were able to strengthen their position not only against Ava but also against Ming China itself. Attempts to impose order in the unruly Shan states proved difficult even for the Chinese. The Ming government's four campaigns (1438–1449) failed to achieve any lasting order. The Chinese troops fruitlessly chased Shan rebels, who simply returned when the Chinese troops left. The Chinese even chased the Shan rebels into Burmese territory, and left only after the Burmese gave up the dead body of the chief. (The event took place in either 1445–1446 according to the Burmese chronicles or 1448–1449, according to the Chinese records.) Faced with more pressing rebellions elsewhere, the Ming government gave up trying to impose imperial order in the Yunnan borderlands, and had to be content with receiving nominal tribute. The Shan states would maintain their space until the mid-16th century. Hanthawaddy–Sukhothai In the south too, the Mon-speaking kingdom based out of Martaban had slowly come into its own. It formally broke away from its overlord Sukhothai in 1330. The southern kingdom's relationship with Sukhothai had always been an opportunistic arrangement from the beginning, designed to secure its rear in case of invasions from Upper Burma. In March 1298, just four years after he became a vassal of Sukhothai, when the Upper Burma ceased to be a threat, Wareru conveniently asked for and received recognition directly from the Mongol emperor as governor even though Sukhothai itself was already a vassal of the Mongols. Indeed, when Sukhothai grew weaker, Martaban seized the Tenasserim coast from Sukhothai in 1319. A decade later, Sukhothai tried to reassert control, reoccupying Tenasserim, and attacking Martaban in 1330. Martaban's defences held. It threw off any formal ties with Sukhothai. Nonetheless, the kingdom remained fragmented into three power centres: the Irrawaddy delta in the west, Pegu in the middle and Martaban in the southeast, each with its own chief, who pledged nominal allegiance to the high king. In 1364, Martaban was seized by a usurper, forcing the king to move the capital permanently to Pegu in 1369. Martaban would be de facto independent for another 20 years until 1388/1389. Forty Years' War Ava's first kings believed that Ava was the Pagan Empire's rightful successor, and attempted to restore the empire. In the south, in 1366, it defeated Toungoo, which had been independent (from Pinya) since 1347. In the northwest, the Shan state of Kale (Kalay) became