Opens a fresh conversation on the study of the Mau Mau rebellion and Kenyan history by arguing that Mau Mau was a nationalist movement rather than a Kikuyu war. Through a critical examination of the Mau Mau oath used to initiate and unite fighters, The Power of the Oath opens a fresh conversation on the study of Mau Mau and Kenyan history. It argues for a historiographical shift inthe framing of the Mau Mau rebellion as a Kikuyu war. Instead, Mickie Mwanzia Koster suggests that Mau Mau was a nationalist movement, embraced by non-Kikuyu communities like the Kamba ethnic group. Incorporating a creative blendof primary sources, including testimonies from ex-Mau Mau participants, survey analysis, archival data, Mau Mau court cases, ceremonial reenactments, and folklore, The Power of the Oath demonstrates how and why the movement was spread, embraced, and internalized. Mwanzia Koster traces the evolution and structure of the Mau Mau oath, examining the British criminalization of the oath, its gendered use, and the purification associated with it, in order to reveal how Mau Mau unfolded in Kenya. Mickie Mwanzia Koster is associate professor of history at the University of Texas, Tyler.