Buddhist Kingdom of Sikkim
Chopel's History in a Nutshell (II)
During the 18th century, the kingdom faced the loss of Chumbi, Haa and Samtse to Tibet and Bhutan, respectively, due to unsuccessful warfare. The Limbu principalities were conquered by the empire of the Gorkha Raja Prithivi Narayan Shah. Too close to the new border with the Gorkha empire, the capital was moved from Rabdentse to Tumlong by Chogyal Tshudpud Namgyal.