DHS's interest in better integrating its legacy agencies has been longstanding, and on several occasions since 2004 the department has identified an approach or vision for establishing a more unified field structure to enhance mission coordination among its component agencies but has not implemented such a structure. As we reported in September 2012, according to senior DHS officials, the fragmentation associated with each operational component having different boundaries for its area of responsibility prompted some in DHS and other stakeholders to promote the idea of a single unified DHS field structure, sometimes referred to as regionalization.