Vamsharaj was made a Kaji on Marwat policy in V.S. 1819. On 20 January 1763, Vamsha Raj Pande won a battle against Mir Qasim, the Nawab of Bengal. On 14 April 1769 A.D., he was the army commander who led attack of Gorkhali side on the Battle of Bhaktapur. After consolidation of Kathmandu valley states, King Prithvi Narayan Shah waged war against western Chaubise Confederacy on 1770 under military leadership of Kaji Bamsharaj, Kaji Kehar Singh Basnyat and Sardar Prabhu Malla and achieved initial success. On 1771, the Gorkhali forces lost the war against Chaubise principalities and Kaji Kehar Singh Basnyat died in the battlefield. In the same war, Bamsharaj was captured by soldiers of Parbat Kingdom as war prisoner. His subordinate commanders Dhaukal Singh Basnyat and Sriharsha Pantha escaped with difficulty after the tough confrontation at Dhor. The document dated Bikram Samvat 1833 Bhadra Vadi 3 Roj 6, shows that he had carried the title of Dewan along with Swaroop Singh Karki. It was the time when he had just returned from the Parbat prison. Chaubisi confederacy attacked Gorkha Kingdom on Sirhanchowk Gadhi at north and established their own position on 2 January 1782 A.D. Commander Garud Dhoj Pant of Tanahun Kingdom launched attack on Gorkhali side with combined army of Lamjung and Parbat and also included soldiers from Kaski, Palpa and Pyuthan. Queen Rajendra Lakshmi Devi wanted ultimate destruction of trade route of Lamjung. Thus, Bamsharaj was called back from his exile in Bettiah to launch attack on Lamjung Kingdom. Queen regentRajendra Laxmi Devi also called up exiled courtier and his rival Swaroop Singh Karki to attack on Lamjung Kingdom. A reconciliation was done with both courtiers. Subsequently, Vamsharaj imposed economic blockade over Lamjung. Bamsharaj's youngest brother Damodar Pande also took part in the attack. Vamsharaj had fought battles against Makwanpur, Timal and Sindhuli in 1762, Kirtipur in 1764, Chihan Danda in 1766, Tanahun in 1770, Pauwa Gadh in 1776, and Lamjung in 1783 A.D.
Death at Bhandarkhal
Bamsha Raj was beheaded on the conspiracy of Queen Rajendra Laxmi with the help of supporters including senior minister Kaji Swarup Singh Karki. In the special tribunal meeting at Bhandarkhal garden, east of Kathmandu Durbar, Swaroop Singh held Bamsa Raj liable for letting the King of Parbat, Kirtibam Malla, to run away in the battle a year before. He was declared guilty and was executed by beheading on the tribunal. Daniel Wright points out that King Rana Bahadur Shah was responsible for giving Bamsha Raj the death penalty. Historian Rishikesh Shah and Ganga Karmacharya claim that he was executed on March 1785. Bhadra Ratna Bajracharya and Tulsi Ram Vaidya claim that he was executed on 21 April 1785. On 2 July 1785, Prince RegentBahadur Shah of Nepal who was aligned to him was arrested.
Title of Premiership
Daniel Wright mentions him as the Mantri-Nayak under the King Rana Bahadur Shah. The document dated Bikram Samvat 1833 Bhadra Vadi 3 Roj 6, shows that he had carried the title of Dewan along with Swaroop Singh Karki. He had a great constant rivalry with Swaroop Singh Karki in the reign of King Pratap Singh Shah.
