The United Nations has been called everything from the best hope of mankind to irrelevant and obsolete. With this much-needed introduction to the UN, Jussi Hanhimäki engages the current debate over the organizations effectiveness as he provides a clear understanding of how it was originally conceived, how it has come to its present form, and how it must confront new challenges in a rapidly changing world. After a brief history of the United Nations and its predecessor, the League of Nations, the author examines the UN´s successes and failures as a guardian of international peace and security, as a promoter of human rights, as a protector of international law, and as an engineer of socio-economic development. Hanhimäki stresses that the UN´s greatest problem has been the impossibly wide gap between its ambitions and capabilities. In the area of international security, for instance, the UN has to settle conflicts--be they between or within states--without offending the national sovereignty of its member states, and without being sidelined by strong countries, as happened in the 2003 intervention of Iraq. Hanhimäki also provides a clear accounting of the UN and its various arms and organizations (such as UNESCO and UNICEF), and he offers a critical overview of how effective it has been in the recent crises in Rwanda and the former Yugoslavia, for example--and how likely it is to meet its overall goals in the future. The United Nations, Hanhimäki concludes, is an indispensable organization that has made the world a better place. But it is also a deeply flawed institution, in need of constant reform.