Gurkha war 1814-16
Gurkhas were ruling in Nepal and from 1767 onwards they extended their power over the hills and valleys of Nepal. They were ruling on Feudal basis and soon became powerful. They marched into the Kumaun and Gangetic Plains and raided in the British Territories.
The British had recently acquired the lands of Nawab of Oudh and Gorakhpur, Sikkim were on the front. The dispute was because of no fixed boundary. The war ended in a defeat of Gurkhas. The British army marched from Patna to Kathmandu and finally dictated the terms of Treaty of Segauli, which defined the English relations with Nepal.
Gurkhas lost Sikkim, the territories of Kumaon and Garhwal, and most of the lands of the Tarai; the British East India Company promised to pay 200,000 rupees annually to compensate for the loss of income from the Tarai region. This remained the definition of India-Nepal relations for a long time.