Before the Mau mau rebellion, he had fought in Burma. Later he became the leader of the Forty Group, an organisation supporting Kenya African Union (KAU). He also founded the Kenya Riigi, a group of illiterate fighters. Mathenge believed in traditional Kikuyu religion. In May 1953 he became the leader of the newly formed Mau Mau military unit Nyeri District Council and Army. His rivalry with field marshal Dedan Kimathi harmed integrity of the Mau mau movement.
On May 30, 2003 a man believed to be Stanley Mathenge, living in Ethiopia, was invited to Kenya by president Mwai Kibaki and was given a hero's welcome by the state. It was soon revealed that the man was Ato Lemma Ayanu, who himself denied being Mathenge. DNA test published four years later proved he was not Mathenge.
- Marshall S. Clough: Mau Mau memoirs: history, memory, and politics Lynne Rienner Publishers, 1998. ISBN 1-55587-537-8
- Abiodun Alao & Christa Hook: Mau-Mau warrior Osprey Publishing, 2006. ISBN 1-84603-024-2
- Robert M. Press: Peaceful resistance: advancing human rights and democratic freedoms.Ashgate Publishing, Ltd., 2006. ISBN 0-7546-4713-7
- Carole Cooper, J. R. A. Bailey & Garth Bundeh: Kenya: The National Epic. Kenway Publications, 1993
- BBC News, May 31, 2003: Doubt cast on Mau Mau hero
- Daily Nation, October 18, 2007: Ayanu Fake, DNA Shows