"October 7 was a complete failure, the IDF (military) failed in fulfilling its mission to protect Israeli civilians," the official said, briefing reporters about the report's contents, on condition of anonymity.

"Too many civilians died that day asking themselves in their hearts or out loud, where was the IDF?"

"The Israel Defense Forces failed to protect Israeli citizens. The Gaza Division was overrun in the early hours of the war, as terrorists took control and carried out massacres in the communities and roads in the area," the military said in the summary of the report released to journalists.

The military acknowledged that it was "overconfident" and had misconceptions about Hamas's military capabilities ahead of the Palestinian militant group's attack, a senior military official said at the same briefing.

The inquiry, which included 77 separate investigations into what transpired in communities, at army bases, and multiple confrontation points around the Gaza periphery, is in the process of being presented to those directly affected.

"We did not even imagine such a scenario," the first military official told journalists, adding that Palestinian militants led by Hamas caught Israel by surprise, not only in terms of the size and scale of the attack, but also its "brutality".

The military probe found that Hamas's attack happened in three waves and at its height more than 5,000 people entered Israel from Gaza.

"The first wave... included more than 1,000 Nukhba (elite force) terrorists who infiltrated under the cover of heavy fire," the summary of the inquiry said.

It added that a second wave included 2,000 militants and third wave was characterised by the arrival of hundreds of militants, along with several thousand civilians.

"In total, approximately 5,000 terrorists infiltrated Israeli territory during the attack," the report said.