After the Raban expedition, Rothangpuia became a British ally. Rothangpuia sent his
karbaris to meet with
Thomas Herbert Lewin, the superintendent of the Chittagong Hill Tracts. They met with Lewin in Kassalong to express the desire to maintain friendly ties with the British and for his people to be trusted as merchants and traders at the frontier markets. Lewin formed an intention to meet with Rothangpuia. After being warned that Rothangpuia had murdered or caused the murder of a sergeant and two frontier policemen in a friendly message, Lewin decided to meet Rothangpuia himself. Lewin ordered his jemadar to form a party to accompany the twenty best men. After two days of encampments and travelling via river, Lewin arrived at Rothangpuia's settlement. The karbaris accompanying Lewin entered into conversation with the
Pasalṭha guarding the settlement with fire-locks. After a deeper travel and climb, Lewin arrived in Rothangpuia's settlement surrounded by 40-50 armed men. Rothangpuia was summoned by Lewin's karbaris. Rothangpuia would formally invite Lewin into the village proper, but without his armed escort, out of consideration for the village's women and children. Lewin proceeded while his men encamped outside Rothangpuia's settlement. Lewin was granted a guest house by Rothangpuia before setting out to gather the neighbouring chiefs to be formally inducted into the family circle. The next day, Lewin was summoned to the chief's house, where Rothangpuia and the other chiefs were assembled. Lewin described Rothangpuia as a physically small, dark, athletic man, with a melancholy cast of countenance and large, stern eyes. Rothangpuia wore no ornaments or insignia typical of a chief apart from fine clothing. After a long pause, Rothangpuia questioned Lewin why he brought an armed escort to his village, which Lewin's karbari translated for him. Leiwn justified it by stating that the journey to his village was dangerous, and now there is no need for it on arrival. Lewin stated his appreciation for Rothangpuia's denials of the raids being committed in the south and confirmed the Anglo-Lushai friendship between them. Rothangpuia did not reply but handed out cups of
zu to him and all the other chiefs. Lewin made a risky remark as he stated, "the prevention of such occurrences (raids) is my duty or, when not preventable, we can punish our enemies, and Rutton Poia knows what I say is true." Lewin states that Rothangpuia took big gulps and stuttered in his response. Rothangpuia asked if the previous superintendent, Captain Magrath, was a magician with a charm against shot and steel. Lewin answered that all British sahibs have this charm. Lewin subsequently retrieved a gun to make an example of his statement. Using a marked bullet which he crossed on, he measured the powder and prepared the shot. He ordered the karbari to shoot him in the chest. After the shot was fired, Lewin feigned a physical shock before placing his hand over his mouth and retrieving the marked bullet from his teeth. Lewin changed the pewter bullet of the Lushai for a waxen ball carefully blackleaded. When the gun fired, the waxen ball was fragmented, and the marked bullet was concealed under Lewin's thumb. Before firing, Lewin covered his eyes to conceal the power and wax from his eyes, but placed the bullet in his mouth. The meeting concluded with Vanlula making a speec,h and a formal alliance was forged offensive and defensive by sacrificing a
mithun. Another incident recounts how when Lewin was in an inquiry with a higher official, Rothangpuia offered via his karbaris to join his settlement. He further offered that each chief will build him a house with many men to follow him on account of his being bulletproof. Another incident recounts a visit to Rothangpuia's village, where a drunk man rudely pushed Rothangpuia. When Lewin questioned why he did not punish the man, Rothangpuia explained that the man was at home and all equal, on the war path, disobedience would be punished with death, but also on account of a man's drunkenness, he is incapable of disrespect. At the start of the
Lushai Expedition, Lewin alerted Rothangpuia to the warlike preparations in the Lushai Hills and not to be alarmed. The assistant political officer, Crouch, was sent to clear a camping ground at Demagiri close to Rothangpuia's village. Rothangpuia, accompanied by two minor chiefs, arrived on 12 November 1871 and offered his support for the cause, providing all assistance within his power. As a result, Lewin introduced Rothangpuia to
Charles Henry Brownlow, who visited his village on 22 November. A gayal was killed in honour of the meeting and a round of drinking
zu. Rothangpuia held a meeting with Lewin after General Brownlow left. Rothangpuia wished to remain neutral because supporting the British would invite hostile powers to destroy him after the expedition. In return for cooperation, Lewin promised Rothanguia that a detachment of police would be placed in his village, which led to Rothanguia's support for the Lushai expedition. As a result, Rothangpuia's wife brought their ten-year-old son and placed his hands folded in Lewin's, as a recognition of him as protector and suzerain. Rothangpuia's involvement in the Lushai Expedition would earn him disfavour with the Howlong chiefs of the Southern Lushai Hills. He was charged with treachery for bringing the English to them and their settlements. Rothangpuia's daughter-in-law, who became a widow, was known as Pakuma rani. Rothangpuia, fearful of the reprisal of the Lushai chiefs, moved him and Pakuma Rani's villages into British territory after they refused to fight his enemies under a non-intervention policy. ==Death==