Sifting through a huge fund of hitherto unexploited sources, Banac demonstrates that the so-called Cominformists, long considered an inconsequential fifth column, in fact represented as much as 20 percent of the party membership. He shows that this fifth column included a variety of oppositional groups within Yugoslav communism who wanted to exploit the crisis for their own purposes. Their aims often diverged, and only from the official Yugoslav perspective could they be said to have constituted a unified opposition. Banac reconstructs the history of the labyrinthine factional struggles that preceded and accompanied the 1948 split and demonstrates that, as always, the national question played the dominant role in Yugoslav politics. After identifying the members of the opposition and mapping its course, Banac recounts the harsh repression of the movement.