His areas of specialization include urbanization, political thought, and media in east Africa, history of decolonization, and history of the Indian Ocean. His research focus is Dar es Salaam, Tanzania, Political History of Tanzania and Kenya. Brennan received his B.A. from the University of Illinois 1991, his M.A. from the University of Alabama in 1994, and his Ph.D. from Northwestern University in 2002.