Ramsey"s historical study examines three cases in which the US Army performed an advisory mission. In Korea during the 1950s, in Vietnam in the 1960s and 1970s, and in El Salvador in the 1980s the Army was tasked to build and advise host nation armies during a time of war. The author makes several arguments about the lessons the Army thought it learned at the time: the need for US advisors: to have language and cultural training; the lesser importance for them of technical and tactical skills training; and the need to adapt US concepts and tactics to local conditions. These lessons are still important and relevant today.