What is the theme in By Way of Deception by Victor Ostrovsky?

One of the most dominant themes of the book is the power of the Mossad and this is Ostrovsky's reason for writing the book. According to the author, the Mossad basically does anything it wants whenever it wants. The head of the agency reports to the prime Minister, but there is no way the Prime Minister can control its activities, and this is the point that Ostrovsky wants to make.