This is a volume for specialists—those who focus on the Communist International (Comintern) and those who study specific Communist parties. The book deals with the encrypted correspondence between Comintern headquarters and various fraternal parties. The cables define the structure and thematic organization of the book. Although the authors provide some introductory context for the cables, a deeper appreciation of the historical context will result in a deeper appreciation of the cables’ importance. As the authors note, the volume is “neither a comprehensive history of the Comintern in the 1930s nor a detailed account of each episode” (p. 5). Rather, the focus is quite sharp. This volume is a condensed English-language version of the volume published in German in 2003 by Fridrikh Firsov and other colleagues. Given that a few earlier volumes in the Annals of Communism Series (Yale University Press) and some other books cover some of the same ground, the Firsov-Klehr-Haynes volume offers no revelations. What it does do is make some intriguing materials available to English-language readers and offer a welter of detail on specific issues. For that it deserves much credit.After a useful introduction, the book consists of ten chapters, all but one of which focuses on West European events. The one exception (chapter seven) is the shortest chapter, examining select cables to and from the Chinese Communist Party. The first chapter provides a clear and useful discussion of the subjects and methods of the Comintern's cipher correspondence and its importance, and chapter two focuses on Soviet subventions to fraternal parties and devotes much attention to detail, such as the amounts given, how money was distributed, and the like. Then the focus turns to Europe. Chapter three discusses the Popular Front, but its focus is primarily on France, particularly communications between Moscow and the leader of the French Communist Party (PCF), Maurice Thoresz. The cables from Thoresz on the political situation in France are interesting, but they offer no revelations.For students of the Spanish Civil War, chapter four makes for intriguing and at times frustrating reading. Joseph Stalin's views on the need for the Spanish Republic to hold new elections, on the departure of the Spanish Communist Party (PCE) from the government, and on the possible merger of the PCE and the Socialist Party allow one to appreciate his odd advice and the PCE's occasional autonomy from Moscow. But the most intriguing cables are from the Italian Communist Palmiro Togliatti, who from mid-1937 was head of the Comintern delegation in Spain and its representative to the PCE. The cipher correspondence underscores Togliatti's rather blunt assessment of the political and military situations, his opposition to certain policy recommendations from Moscow, and his personal feuds with other Soviet personalities in Spain. But knowledgeable readers will be frustrated by the editors’ misrepresentations of some Spanish realities, the most notable being their claim that the Workers’ Party of Marxist Unification (POUM—the Communist party in Spain) “had supported the Popular Front” and that Republican “government forces … murdered Andrés Nin, [POUM's] chief figure” (p. 81). One need only read POUM publications from 1937 to appreciate the party's hostility to the Popular Front. Nin was murdered not by the Spanish government but by assassins of the Soviet state security organs.The cipher correspondence regarding the International Brigades in Spain, which is chapter five's focus, makes clear the Comintern's active role in directing fraternal parties to recruit volunteers and acquire weapons for Spain. No less engaging is André Marty's and others’ bleak assessment of the quality of the volunteers. But here, too, the authors make some obvious gaffes. After discussing the boastful behavior of General Kleber (the nom de guerre of Manfred Stern) covered in the Spanish press in November 1936, of which Moscow disapproved, they claim that Kleber's foreign citizenship (he was a Soviet military intelligence officer) “provided justification of Franco's acceptance of German and Italian aid for his forces.” By that time, German planes controlled most of the skies over Spain, and more than 60,000 Italian troops were on Spanish soil.Chapter six (“The Comintern and the Terror”) is the oddest and most revealing chapter. Various published volumes have documented the Comintern's direction of the international anti-Trotskyist campaign, including Georgi Dimitrov's role in recalling his charges from abroad to face arrest and worse, and the Feuchtwanger affair, all of which are in this chapter. The cipher correspondence presented in the chapter augments these other treatments. But the tone and language here reveal some of the authors’ underlying political assumptions, which set the interpretive tone for the entire volume.Chapters eight and nine focus on the period leading up to the Nazi-Soviet Pact and the war. Even for readers who know this period well, these chapters provide an abundance of intriguing details. Of special interest is the cipher correspondence that conveys the confusion among Comintern leaders and the various fraternal parties following the announcement of the Nazi-Soviet Pact and their obvious relief after the Axis invasion of the USSR, not because of the invasion but because Communists could return to the anti-fascist policies that had generated popular support for European and North American Communist parties.The more one knows about the period, the more one can appreciate the importance of some of the cables, not because they reveal something new but because of the rich detail they add to our understanding. But such knowledge is essential because the two chapters consist of a series of snapshots. The chapter on the Nazi-Soviet Pact presents materials on the instructions sent to various parties (e.g., of the Baltic states, Bulgaria, Germany, Czechoslovakia) and in the process conveys a sense of the confusion that riddled the fraternal parties. The chapter on the war offers some intriguing materials on communications between Yugoslavia and Moscow, but it offers even more “snapshots” as it moves from materials on Yugoslavia to the creation of the Polish Workers Party, the murder of the Polish Communist Marceli Nowotko, the Warsaw ghetto uprising, the PCF, and the Red Orchestra, to name just the most notable discussions.Despite some of this review's complaints, the book is a valuable source for specialists, not only for the cipher correspondence it presents but also for other materials, such as the various codenames used by Comintern personnel and operatives and the weaving together of the correspondence and other primary sources (e.g., Dimitrov's diary and correspondence). For scholars of the Comintern, Soviet intelligence, and the national Communist parties discussed, this is more than a valuable volume; it is a basic reference work. For this, we owe the authors, especially Firsov, the main author, many sincere thanks.