As world population increases, disasters, both natural and man-made, show a correspondingly greater toll of human lives. Existing rescue services are inadequate with regard to major disasters. They are unable to centralize and secure the relevant expertise and to control all rescue operations involving the movement of men, materials and messages within the disaster area. Immediately after the disaster strikes, the problem of the logistic mobilization of resources and coordination of rescue, first aid and relief work emerges as a first priority. Associated with this activity may be the prevention of secondary effects such as flood, fire or explosion which are also liable to trap and kill people. Lack of coordination in relief operations has a detrimental effect on longer term reconstruction. Misdirected relief operations may also deter the less skilled yet able-bodied from participating in reconstruction. Unless there is adequate planning in the situating of relief stores, camps and emergency housing, they may be placed in areas essential for early reconstruction or in areas liable to flooding or difficult to service with water and sewage disposal.
Before 1900, disaster relief consisted mainly of emergency grants of food, clothing and medical care, and the provision of mass shelter through hastily organized local committees. In the 20th century, disaster relief has become one of the chief activities of the International Red Cross Committee (war disasters) and the League of Red Cross Societies (natural disasters). In 1971, the UN General Assembly established the UN Disaster Relief Coordinator office (UNDRO) with mandate to promote disaster prevention and preparedness and to coordinate relief assistance at the international level. Organizations such as the Pan American Health Organization, regional office for the Americas of the World Health Organization, established disaster preparedness as a high priority in their development activities.
Logistics often present the most serious obstacle to quick assistance. Many developing countries have poor land communication to isolated areas and lack the resources to hold sufficient vehicles and aircraft in readiness for emergency use. International assistance is often hampered by lack of reliable and rapid assessment of needs, resulting in inappropriate or obsolete relief supplies. The use of foreign assistance may be very seriously delayed or rendered impossible by political sensitivity to over-flying and landing arrangements for military aircraft or providing visas for the movement of foreigners within the frontiers of a State.