Mibambwe III Sentabyo died along with his only known son from a Ndorwa woman, leading many to believe there was no heir apparent. However, unbeknownst to them, he had another son, Yuhi Gahindiro in Rwanda.
The death of Mibambwe III Mutabazi Sentabyo invigorated Gatarabuhura, who quickly crossed the Nyabarongo River westwards to claim recognition as the true heir to Kigeli III Ndabarasa. His supporters welcomed him enthusiastically, while his opponents scrambled to counter this move.
Before leaving Gisaka, Gatarabuhura had requested armed escorts from Kimenyi IV to prepare for any eventuality. Leading his warriors, he crossed the Nyabarongo River and entered Nduga (now Kamonyi, Muhanga, and Ruhango districts).
Advised by sages not to fight over a woman and her baby son, Gatarabuhura sent assassins to kill them instead. However, a spy informed the young monarch’s court of the plot.
In feudal Rwanda, liberators were common. Kiyange, a servant at the court, offered to replace the queen mother, while Nyiramuhanda offered her son, Rubanzangabo, to replace Yuhi IV Gahindiro. The assassins, misled by these decoys, killed the liberators instead. They returned to Gatarabuhura, claiming victory.
The next day, royal drums sounded at the usual time at the court, signaling Yuhi IV Gahindiro's enthronement at Mutakara in Ruhango district. Feeling betrayed, Gatarabuhura's supporters resorted to arms.
Prince Semugaza, accompanying Gatarabuhura, became a pivotal figure. Initially hesitant to engage in battle, he ordered his warriors to attack when he saw Yuhi IV Gahindiro's men retreating.
Defeated, Gatarabuhura tried to escape to Gisaka, hoping for assistance at Kinyambi. However, instead of help, he was taken prisoner and delivered to Yuhi IV Gahindiro's court, where he was condemned and thrown into the famous well of Rwabayanga in Bugesera district.
The queen mother governed until Yuhi IV came of age. Despite emerging plots, Prince Semugaza returned to Ndorwa. During Yuhi IV's reign, struggles with Gisaka, Ndorwa, Buhunde (now in DRC), and Burundi continued. Prince Semugaza, leading his militia, restored Rwanda's dignity by attacking Bunyabungo (now in DRC-Bukavu) through Rubavu-eastern DRC.
Despite these conflicts, Yuhi IV's reign is considered the most peaceful in history. He died of an unknown illness, referred to as "urwagatandabazimu,” and was buried in Kayenzi, formerly Tumba commune, now in Rulindo district.