The good relationship of both sides was not maintained for long before fresh wars broke out, as each side sought stronger power along the mutual border and more military and economic benefits. The Tubo kingdom took steps to combine with Tujishi and Nanzhao respectively to the northern and southeastern sides of its territory. In 751, Gelofen, King of Nanzhao, pledged allegiance to the Tubo kingdom and the letter conferred on the former the title of Tsampo Zong, meaning brother of Tsampo. The united forces of the Tubo kingdom and Nanzhao posed a serious threat to the Tang Dynasty. The scale of war was incessantly upgraded and neither side was willing to give in. In the end, some military leaders with huge forces emerged in the border area and gained military control. Probably in 754, Motongbuze and Nammeise, both serving as Dalun of the Tubo kingdom, openly staged a rebellion and killed Tsampo Tride Zhotsan. It took the Tubo kingdom over one year to suppress the uprising, after which the leaders of the rebellion were killed, their properties confiscated and their relatives banished to remote areas. Trisung Detsan, who was only thirteen years old, took the throne. At that time, the armed forces of the Tubo kingdom and the Tang Dynasty changed greatly, as the latter was embroiled in a rebellion led by An Lushan and Shi Siming. Tang Xuanzong fled to Sichuan from Chang'an, and most of army forces resisting the Tubo army were dispatched to put down the uprising, leading to weak resistance toward the Tubo army's attack. Taking this opportunity, the Tubo army occupied most areas of Longyou, the Hexi Corridor and four towns of Anxi. In October of 763, when the emperor and ministers of the Tang Dynasty fell into disputes, the Tubo army grasped the opportunity to dispatch 200,000 soldiers to proceed toward Chang'an. On hearing the news, Tang Daizong fled in panic toward Shanzhou. During the fifteen days that it controlled Chang'an, the Tubo army helped Prince Guangwu Li Chenghong, Princess Jincheng's nephew, ascend to the throne and appointed hundreds of military and civilian officials. However, disease soon spread through the Tubo army, probably due to the hot weather of Chang'an to which it was unaccustomed. At that time, the forces of Prince Qin of the Tang Dynasty were approaching Chang'an. In order to avoid large casualties, the Tubo army made the choice to retreat. During the reign of Trisung Detsan, the territory of the Tubo kingdom expanded greatly: On the eastern side, it bordered on the Tang Dynasty at Mt Long, and several times it advanced into Baoji to threaten Chang'an; On the northern side, it stretched to Mt Helan in today's Ningxia Hui Autonomous Region and Huihe; On the southern side, it annexed the Nanzhao kingdom; On the western side it had the Four Towns of Anxi. In Central Asia, it could compete well with the empire of Dashi (Persia). Tibetan historical records state the Tubo kingdom once advanced the northern bank of the Ganges. So, it is no exaggeration to state that, at the time of Trisung Detsan, the area of the Tubo Kingdom reached over half a million kilometers.