The U.S. State Department Central Files are the definitive source of American diplomatic reporting on political, military, social, and economic developments throughout the world in the 20th century. Concentrating exclusively on those Central Files that have not been microfilmed by the National Archives or other publishers, UPA's microfilm editions of the Central Files nonetheless dwarf the State Department's very selective volumes of the Foreign Relations of the United States (FRUS). Containing less than one percent of the material in the Central Files, FRUS focuses on U.S. relations with individual countries but does not include coverage of many of the key topics to which the majority of the original files are devoted. Each part of the Central Files contains a wide range of materials from U.S. diplomats in foreign countries: special reports on political and military affairs; studies and statistics on socioeconomic matters; interviews and minutes of meetings with foreign government officials; court proceedings and other legal documents; full texts of important letters, instructions, and cables sent and received by U.S. diplomatic personnel; voluminous reports and translations from foreign journals and newspapers; and countless translations of high-level foreign government documents. The U.S. State Department records for Nicaragua from 1945 through 1959 chronicle the eventful later career of Anastasio Somoza to his assassination in 1956. Cables, reports, and many other documents record the consolidation of virtually absolute political, economic, and military power as the position of the presidency became, in Somoza's hands, the means of strengthening his personal rule and establishing a political dynasty. Nicaragua's relations with its Central and South American neighbors-and with the United States-are also the subject of extensive State Department coverage. In Costa Rica, Mexico, Cuba, and Argentina the presence of Nicaraguan exile groups working to overthrow Somoza led to inevitable tensions, and the increasing strength of the Somoza dynasty bolstered by mutual defense arrangements with the United States-was a major cause of regional concern. Much of the current unrest in Latin America is rooted in the historical legacy of these years.