This thesis is a case study of CNDD-FDD, a former rebel group turned political party in Burundi. The analysis will take off in 1994 when the rebel group is established and concluded today in 2019 with CNDD-FDD being an increasingly authoritarian one-party ruler. This thesis adds to the recent resurgence of literature focused on ideology and how it is changed and reshaped in the post-conflict setting. The focus of the analysis is therefore how the ideology in CNDD-FDD changes over time. The analysis will use primary sources from the actor for capturing their ideology, together with secondary sources for creating context. The analysis uses a newly developed theoretical framework by Sindre (2018) consisting of two dimensions, a conflict cleavage dimension and a peacebuilding dimension, with the objective of capturing ideological change in CNDD-FDD as well as developing the framework. A negative shift on both dimensions are observed over time, and a new issue of openness is suggested to be added to the peacebuilding dimension.