When Solzhenitsyn published The Oak and the Calf, the autobiographical account of his writing career, he omitted a substantial section in which he named helpers of his who would be in jeopardy if the Soviet authorities knew of their activities. This material was serialized under the title Invisible Allies after the Soviet Union disappeared, and in 1996 it was included in an expanded edition of The Oak and the Calf where it takes its rightful place as the Fifth Supplement. The definitive biography of Solzhenitsyn, whenever it is written, will draw heavily on this information. With its revelation of previously unknown episodes and the dramatis personæ engaged in them, Invisible Allies significantly enhances the sense that the man's life, in and of itself, took on the contours of a work of art.
Reading Invisible Allies is greatly enriched by reading in tandem The Solzhenitsyn Files, the now-declassified records of the efforts by top Soviet officials to handle the recalcitrant author. These two volumes chart the same confrontation from opposite sides—versions written by the calf and by the oak, as it were. Among the many perverse pleasures the regime's files afford is the realization of how successfully Solzhenitsyn's allies remained invisible, as the writer and his confederates outfoxed the befuddled authorities.
Invisible Allies ends with a sensational appendix containing the reminiscences of a repentant KGB man who participated in a failed operation to assassinate Solzhenitsyn in 1971.
-- from The Soul and Barbed Wire, by Edward E. Ericson, Jr. and Alexis Klimoff