Hours of tapes from the office of former Israel Defense Forces Chief of Staff Gabi Ashkenazi are at the heart of the state comptroller's investigation into the so-called Harpaz affair, an alleged plot to thwart Maj. Gen. Yoav Galant's chances of heading the IDF.

State Comptroller Micha Lindenstrauss and his investigators have been listening to these tapes for months. It is not clear how many of the tapes are relevant to the investigation or to what degree, if at all, Ashkenazi was involved in the recorded conversations, but they have apparently shed new light on the case.

The tapes are the main reason the comptroller's draft report on the affair, which has been roiling the defense establishment for over a year, has been delayed. But it will apparently be completed in a month or so. The final report, issued after those affected have had a chance to respond to the draft, will likely follow three or four months later.

Various people involved in the probe say Ashkenazi is likely to suffer the most damage from the report, which will also address his fraught relationship with Defense Minister Ehud Barak. But the report is also expected to criticize Barak and his staff over how they handled both the tension with Ashkenazi and the process of selecting a new chief of staff.

Haaretz has spoken with several witnesses summoned by the comptroller in recent months, and they report being shown transcripts of conversations they held in or with Ashkenazi's office, both in person and by telephone. In some cases, they were even shown the tapes themselves. They therefore believe these tapes will play a key role in the report.

The Harpaz affair erupted in August 2010, when Channel 2 television revealed a document that purportedly detailed a plan to smear Ashkenazi and his associates, and thereby further Galant's chances in the race to be the next chief of staff. Galant was thought to be Barak's preferred choice, but Ashkenazi favored either Benny Gantz or Gadi Eizenkot.

The document bore the logo of Eyal Arad's public relations firm, and Arad complained to the police. The ensuing probe determined that it had been forged by Lt. Col. (res. ) Boaz Harpaz, a former IDF officer close to Ashkenazi.

It also found that the document had made its way to Channel 2 from Ashkenazi's office, albeit through several intermediaries. Harpaz initially confessed to the forgery but has since retracted his confession.

Galant was subsequently appointed chief of staff, but the appointment was canceled before it took effect due to allegations that he had improperly appropriated state land near his home. Gantz was then appointed in February 2011.

In November 2010, Lindenstrauss began his probe. His staff has interviewed hundreds of witnesses.

In June 2011, Harpaz also agreed to testify. Since he isn't a civil servant, he wasn't obligated to do so. Harpaz has testified five times, and it seems likely that some of his testimony hurt Ashkenazi.

At one point during the probe, someone in Ashkenazi's office showed the comptroller's staff a transcript of a telephone call between an Ashkenazi aide and someone in Barak's office, thereby alerting the investigators to the fact that the tapes existed.

A few months after Ashkenazi left office, the comptroller asked Gantz, the new chief of staff, for all the tapes made by Ashkenazi's office during the relevant months. After consulting then-Military Advocate General Avichai Mandelblit, Gantz acquiesced.

Taping important operational discussions has long been standard practice in the chief of staff's office and those of other senior IDF commanders, so that documentation would be available if it was ever needed. But when former Chief of Staff Dan Halutz took office in 2005, he adopted the practice of taping almost all of the office's conversations, which was the norm in his previous post at the air force. Ashkenazi continued this practice, which is how the current trove came to exist. No similar trove exists from Barak's office, which apparently taped only operational discussions.

Several IDF officers told Haaretz that while the recordings were legal, they were surprised to discover that conversations they thought were confidential had in fact been taped.