The cluster approach designates individual agencies as ‘sector leaders’ to coordinate operations in specific areas to try to plug those newly identified gaps. The cluster approach was conceived amid concerns about coordination and capacity that arose from the weak operational response to the crisis in Darfur in 2004 and 2005, and the critical findings of the Humanitarian Response Review (HRR) commissioned by the then ERC, Jan Egeland. Egeland called for strengthening leadership of the sectors, and introduced the concept of "clusters" at different levels (headquarters, regional, country and operational)’.