sentences:  On 20 August 2008 Umaru Yar'Adua replaced Azazi with Paul Dike as CDS and announced Azazi's retirement from military service.Azazi emerged from retirement to assume the National Security Adviser (NSA) post as a civilian.He inherited a range of challenges from extremists, including the militant Movement for the Emancipation of the Niger Delta (MEND) in his native region, and the rise of a new violent Islamist group called Boko Haram, which first emerged in 2009.