The availability of an integrated code base is often taken for granted in common reengineering literature. In this paper, we report on the approaches used by the EDS eFlex project team to gain better control over a large, technology-heterogeneous code base in the context of the reengineering of a multi-million line software system. Specifically in the context of geographically dispersed teams, controlling the code base is a prerequisite for efficient evolution. After enlisting key evolution impediments emerging in the integration of software systems that each have their own code bases, we characterize our activities in unifying these code bases.