The cluster approach operates on the global and local levels. At the global level, the approach is meant to build up capacity in eleven key ‘gap’ areas by developing better surge capacity, ensuring consistent access to appropriately trained technical expertise and enhanced material stockpiles, and securing the increased engagement of all relevant humanitarian partners. At the field level, the cluster approach strengthens the coordination and response capacity by mobilizing clusters of humanitarian agencies (UN/Red Cross-Red Crescent/IOs/NGOs) to respond in particular sectors or areas of activity, each cluster having a clearly designated and accountable lead, as agreed by the HC and the Country Team. Designated lead agencies at the global level both participate directly in operations, but also coordinate with and oversee other organizations within their specific spheres, reporting the results up through a designated chain of command to the ERC at the summit. However, lead agencies are responsible as ‘providers of last resort’, which represents the commitment of cluster leads to do their utmost to ensure an adequate and appropriate response in their respective areas of responsibility. The cluster approach was part of a package of reforms accepted by the IASC in December 2005 and subsequently applied in eight chronic humanitarian crises and six sudden-onset emergencies. However, the reform was originally rolled out and evaluated in four countries: DRC, Liberia, Somalia and Uganda.