Cyilima II Rujugira, father to Kigeli III Ndabarasa (1708-1741), died without receiving his burial rites promptly. Kigeli III Ndabarasa, who had already been co-reigning alongside his father, ascended to full kingship.
His mother had passed away, so he appointed Nyiratunda, a cousin of his mother Rwesero, as his queen mother. Kigeli appointed his son Butwatwa to command the Ababito militia, but the prince died shortly after, and the responsibility was passed to Kigeli's brother Semugaza.
Although Kigeli III was initially a subordinate to his father, his ambitions were fixed on conquering and annexing Ndorwa (present day Nyagatare, Gicumbi, Gatsibo and parts of Western Uganda).
Upon his father's death, Kigeli III launched an attack on Ndorwa, successfully conquering it. He chose to remain in Ndorwa until his death, making only sporadic visits back to Rwanda.
Kigeli III Ndabarasa did not forget the small kingdom of Mubali, ruled by Biyoro and his mother Nyirabiyoro, whose capital was on an island in a lake. To lure them off the island, Kigeli pretended to form an alliance with Biyoro and sought the hand of Biyoro's daughter, Nyabugondo, in marriage. Biyoro agreed, but Nyabugondo went as a liberator, never meeting the Rwandan king.
With his flotilla ready, Kigeli III positioned himself in Rubona, near the Mubali border, now in Gatsibo district (formerly Murambi commune). He arranged a meeting with Biyoro and his mother.
The plan partially succeeded: the queen mother was captured, but Biyoro, warned by survivors, turned back and fled. Kigeli's flotilla seized Mubali's island capital, capturing its drum emblem and dispersing the defenders. Biyoro fled to Karagwe.
Learning of Biyoro's flight, Kigeli sent militia and messengers to the king of Karagwe, warning him of the taboo against Rwandan kings attacking Karagwe. The king, aware of Kigeli's prowess, handed Biyoro over to Rwandan warriors.
When Biyoro arrived in Rubona, his mother, who had refused food, asked Kigeli for sustenance, lamenting, "Ngaye inda, ngaye Ndagara—which can be loosely translated as eating food offered by her captors and betrayal by the king of Karagwe she regarded as a son given the long time partnership between Karangwe kingdom and Mubali kingdom.
This phrase showed her belief that hunger makes one bow to the enemy. With the king and the drum emblem captured, Mubali was annexed to Rwanda.
Kigeli III Ndabarasa was related to Kimenyi IV Getura, making him a likely candidate to attack Gisaka. However, this did not happen, possibly due to divinatory oracles.
While Kigeli III was in Munyaga (now Rwamagana district), Abakemba militia under Ruzamba, son of Sharangabo, attacked and defeated Kimenyi IV Getura. Kimenyi IV, calling Kigeli his son, sought his help. Kigeli ordered Ruzamba, who resisted, to return, necessitating the arrest of his maternal uncle to ensure compliance.
Rwandans grew weary of Kigeli III Ndabarasa's prolonged stay in Ndorwa. He delegated his son Mutabazi, unaware of being heir apparent, to represent him, allowing royal drumming to be heard again. Prince Mutabazi held full authority.
Despite numerous efforts to bring Kigeli III Ndabarasa back to Rwanda as he aged, he refused. He died of disease, which was kept secret from Rwandans. He was buried in Rutare on Munanira hill, now in Rutare sector, Gicumbi district.