A careful campaign of deception ensured Israel was caught off guard when the Palestinian Islamist group Hamas launched its devastating attack, enabling a force using bulldozers, hang gliders and motorbikes to take on the Middle East's most powerful army.

Saturday's assault, the worst breach in Israel's defences since Arab armies waged war in 1973, followed two years of subterfuge by Hamas that involved keeping its military plans under wraps and convincing Israel it did not want a fight.

While Israel was led to believe it was containing a war-weary Hamas by providing economic incentives to Gazan workers, the group's fighters were being trained and drilled, often in plain sight, a source close to Hamas said.

This source provided many of the details for the account of the attack and its buildup that has been pieced together by Reuters. Three sources within Israel's security establishment, who like others asked not to be identified, also contributed to this account.

"Hamas gave Israel the impression that it was not ready for a fight," said the source close to Hamas, describing plans for the most startling assault since the Yom Kippur War 50 years ago when Egypt and Syria surprised Israel and made it fight for its survival.

"Hamas used an unprecedented intelligence tactic to mislead Israel over the last months, by giving a public impression that it was not willing to go into a fight or confrontation with Israel while preparing for this massive operation," the source said.

Israel concedes it was caught off guard by an attack timed to coincide with the Jewish Sabbath and a religious holiday. Hamas fighters stormed into Israeli towns, killing 700 Israelis and abducting dozens. Israel has killed more than 400 Palestinians in its retaliation on Gaza since then.

"This is our 9/11," said Major Nir Dinar, spokesperson for the Israeli Defence Forces. "They got us."

"They surprised us and they came fast from many spots - both from the air and the ground and the sea."

Osama Hamdan, the Hamas representative in Lebanon, told Reuters the attack showed Palestinians had the will to achieve their goals "regardless of Israel's military power and capabilities."

'THEY RAN RIOT'

In one of the most striking elements of their preparations, Hamas constructed a mock Israeli settlement in Gaza where they practiced a military landing and trained to storm it, the source close to Hamas said, adding they even made videos of the manoeuvres.

"Israel surely saw them but they were convinced that Hamas wasn't keen on getting into a confrontation," the source said.

Meanwhile, Hamas sought to convince Israel it cared more about ensuring that workers in Gaza, a narrow strip of land with more than two million residents, had access to jobs across the border and had no interest in starting a new war.

"Hamas was able to build a whole image that it was not ready for a military adventure against Israel," the source said.

Since a 2021 war with Hamas, Israel has sought to provide a basic level of economic stability in Gaza by offering incentives including thousands of permits so Gazans can work in Israel or the West Bank, where salaries in construction, agriculture or service jobs can be 10 times the level of pay in Gaza.

"We believed that the fact that they were coming in to work and bringing money into Gaza would create a certain level of calm. We were wrong," another Israeli army spokesperson said.

An Israeli security source acknowledged Israel's security services were duped by Hamas. "They caused us to think they wanted money," the source said. "And all the time they were involved in exercises/drills until they ran riot."

As part of its subterfuge in the past two years, Hamas refrained from military operations against Israel, even as another Gaza-based Islamist armed group known as Islamic Jihad launched a series of its own assaults or rocket attacks.

NO INKLING

The restraint shown by Hamas drew public criticism from some supporters, again aimed at building an impression that Hamas had economic concerns not a new war on its mind, the source said.

In the West Bank, controlled by Palestinian President Mahmoud Abbas and his Fatah group, there were those who mocked Hamas for going quiet. In one Fatah statement published in June 2022, the group accused Hamas leaders of fleeing to Arab capitals to live in "luxurious hotels and villas" leaving their people to poverty in Gaza.

A second Israeli security source said there was a period when Israel believed the movement's leader in Gaza, Yahya Al-Sinwar, was preoccupied with managing Gaza "rather than killing Jews". At the same time, Israel turned its focus away from Hamas as it pushed for a deal to normalise relations with Saudi Arabia, he added.

Israel has long prided itself on its ability to infiltrate and monitor Islamist groups. As a consequence, the source close to Hamas said, a crucial part of the plan was to avoid leaks.

Many Hamas leaders were unaware of the plans and, while training, the 1,000 fighters deployed in the assault had no inkling of the exact purpose of the exercises, the source added.

When the day came, the operation was divided into four parts, the Hamas source said, describing the various elements.

The first move was a barrage of 3,000 rockets fired from Gaza that coincided with incursions by fighters who flew hang gliders, or motorised paragliders, over the border, the source said. Israel has previously said 2,500 rockets were fired at first.

Once the fighters on hang-gliders were on the ground, they secured the terrain so an elite commando unit could storm the fortified electronic and cement wall built by Israel to prevent infiltration.

The fighters used explosives to breach the barriers and then sped across on motorbikes. Bulldozers widened the gaps and more fighters entered in four-wheel drives, scenes that witnesses described.

'HUGE FAILURE'

A commando unit attacked the Israeli army's southern Gaza headquarters and jammed its communications, preventing personnel from calling commanders or each other, the source said.

The final part involved moving hostages to Gaza, mostly achieved early in the attack, the source close to Hamas said.

In one well-publicised hostage taking, fighters abducted party-goers fleeing a rave near the kibbutz of Re'im near Gaza. Social media footage showed dozens of people running through fields and on a road as gunshots were heard.

"How could this party happen this close (to Gaza)?" the Israeli security source said.

The Israeli security source said Israeli troops were below full strength in the south near Gaza because some had been redeployed to the West Bank to protect Israeli settlers following a surge of violence between them and Palestinian fighters.

"They (Hamas) exploited that," the source said.

Dennis Ross, a former Middle East negotiator who is now at the Washington Institute for Near East Policy, said Israel had been distracted by violence in the West Bank, leading to a "thin, under-prepared presence in the south."

"Hamas probably succeeded beyond their expectation. Now they will have to deal with an Israel determined to decimate them," he said.

Retired General Yaakov Amidror, a former national security adviser to Prime Minister Benjamin Netanyahu, told reporters on Sunday the assault represented "a huge failure of the intelligence system and the military apparatus in the south."

Amidror, chairman of the National Security Council from April 2011-November 2013 and now senior fellow with the Jerusalem Institute for Strategy and Security, said some of Israel's allies had been saying that Hamas had acquired "more responsibility".

"We stupidly began to believe that it was true," he said. "So, we made a mistake. We are not going to make this mistake again and we will destroy Hamas, slowly but surely."