Certain parts of the world, including the Sahel, the Horn of Africa (plus Yemen), the Great Lakes region of Central Africa, and parts of Central Asia, face extraordinary challenges as the result of the combination of extreme poverty, weak infrastructure, chronic violence, rapid population growth, and inherently difficult geographical conditions (such as being landlocked, small island states, extremely arid, highly vulnerable to droughts and floods, and/or having a high burden of communicable diseases such as malaria). Countries facing these tremendous and interconnected challenges need special international support, including timely and adequate external assistance. They also need a regional focus, since many of the problems (weak transportation, cross-border nomadism, displaced populations, droughts, epidemics, and conflicts) occur at the regional scale and must be addressed in part at that scale.