The authority of Toungoo Dynasty with the capital at Ava had long been in decline when the Mon of Lower Burma broke away in 1740, and founded the Restored Hanthawaddy Kingdom with the capital at Pegu . The "palace kings" at Ava had been unable to defend against the Manipuri raids, which began in 1724 and had been ransacking increasingly deeper parts of Upper Burma. Ava failed to recover southern Lan Na  that revolted in 1727, and did nothing to prevent the annexation of northern Shan states by Qing China in the mid-1730s. King Mahadhammaraza Dipadi of Toungoo made feeble efforts to recover Lower Burma in the early 1740s, but by 1745, Hanthawaddy had successfully established itself in Lower Burma. The low-grade warfare between Ava and Pegu went on until late 1750, when Pegu launched its final assault, invading Upper Burma in full force. By early 1752, Peguan forces, equipped with French arms, had reached the gates of Ava. Upayaza, the heir apparent of Hanthawaddy throne, issued a proclamation, summoning the administrative officers in the country north of the city to submit, and swear allegiance to the king of Hanthawaddy. Many regional chiefs of Upper Burma faced a choice: whether to join the Hanthawaddy forces or resist occupation. A few chose to cooperate. But many others chose to resist.. How many years after the Manipuri raids began did southern Lan Na?