The treaty of Sugauli, which has been one of the main cause for Nepal's loss in territory was signed in 2 December,1815 between East India Company and King of Nepal following the Anglo-Nepalese War 1814-1816.
Under the treaty, Nepal had lost one-third of its territory which was previously won by King of Nepal within last 25 years.Those territories which are now renowned by states of India includes Darjeeling to the South-east, whole of Sikkim to the east, whole of Mithila to south, Nainital to the south-west and Kumaon Kingdom, Gadhwal Kingdom and Bashahar to the west