Msiri adopted the local title of Mwami (chief) and began a systematic campaign of conquest. He possessed two decisive advantages: firearms and a core of loyal, well-armed Nyamwezi warriors. While a few muskets had trickled into the interior, Msiri managed to secure a relatively steady supply from Arab-Swahili traders, giving his small force overwhelming firepower against local armies armed with spears, bows, and iron-tipped arrows. His warriors, known as the Tutume ("the Thundering Ones"), became feared across the savanna. Between 1856 and 1870, Msiri systematically subjugated the various Luba, Lunda, Sanga, and other local groups. He played rival chiefs against each other, offered alliances that turned into vassalage, and annihilated those who resisted. He did not simply destroy; he incorporated. Conquered chiefs were allowed to retain local authority as long as they paid tribute in copper, ivory, and slaves, and recognized Msiri’s ultimate sovereignty. He adopted local customs, including the Lunda concept of bulopwe (sacred kingship), and married dozens of daughters of defeated or allied chiefs, weaving a vast web of kinship-based alliances that bolstered his rule.
Leopold sent a series of expeditions to secure Msiri’s submission. The first, led by a German adventurer, Hermann von Wissmann, failed to even meet the king. The second, the Stairs Expedition of 1891, would be decisive. Commanded by the arrogant and ruthless British-Canadian mercenary Captain William Grant Stairs, the expedition was a small, heavily armed force of Europeans (including a Belgian, a Polish-born engineer, and a Swiss doctor) and several hundred African mercenaries, mostly Zanzibari askaris.
The Yeke warriors were stunned. Their god-king, the man they believed to be invincible, lay dead. Stairs ordered Msiri’s body decapitated and the head hoisted on a pole in front of Bunkeya as a gruesome warning. He then forced the Yeke elders to sign a "treaty" ceding the kingdom to Leopold. The Stairs Expedition then looted Bunkeya, stripping it of its copper treasures, ivory, and the legendary mwano copper cross, which was broken up and shipped to Europe. The Yeke Kingdom collapsed with shocking speed. The empire, so dependent on the personal charisma, strategic genius, and ruthless authority of Msiri, could not survive him. His sons and successors, including Mukanda-Bantu and his daughter, the formidable Mwami (Queen) Maria Fwasa, led desperate resistance for a few years, but they were overwhelmed by the superior firepower and brutal counterinsurgency tactics of the Congo Free State's Force Publique. Many Yeke fled south across the Luapula River into what is now Zambia, where their descendants live today, preserving their distinct identity and the memory of Msiri.
The legacy of the Yeke Kingdom is complex. For decades, European colonial historians dismissed it as a brutal, parasitic slave state—a product of "Arab" influence on the "primitive" interior. This view, steeped in colonial racism, ignored the sophisticated indigenous state-building that Msiri achieved. He did not copy an external model; he hybridized Nyamwezi military organization with Luba-Lunda concepts of sacred kingship and economic control.