How did Israel’s intelligence network fail?

But Israel's eyes appeared to have been closed in the lead-up to an unprecedented onslaught by the militant Hamas group, which broke down Israeli border barriers and sent hundreds of militants into Israel to carry out a brazen attack that has killed hundreds and pushed the region toward conflict.

Israel's intelligence agencies have gained an aura of invincibility over the decades because of a string of achievements. Israel has foiled plots seeded in the West Bank, allegedly hunted down Hamas operatives in Dubai, and has been accused of killing Iranian nuclear scientists in the heart of Iran. Even when their efforts have stumbled, agencies like the Mossad, Shin Bet, and military intelligence have maintained their mystique.

But the weekend's assault, which caught Israel off guard on a major Jewish holiday, plunges that reputation into doubt and raises questions about the country's readiness in the face of a weaker but determined foe.

“This is a major failure,” said Yaakov Amidror, a former national security adviser to Prime Minister Benjamin Netanyahu. “This operation actually proves that the (intelligence) abilities in Gaza were no good.”

Rear Adm. Daniel Hagari, the chief military spokesman, acknowledged the army owes the public an explanation. But he said now is not the time. “First, we fight, then we investigate,” he said.

Some say it is too early to pin the blame solely on an intelligence fault. They point to a wave of low-level violence in the West Bank that shifted some military resources there and the political chaos roiling Israel over steps by Netanyahu's far-right government to overhaul the judiciary. The controversial plan has threatened the cohesion of the country's powerful military.

But the apparent lack of prior knowledge of Hamas' plot will likely be seen as a prime culprit in the chain of events that led to the deadliest attack against Israelis in decades.

Amir Avivi, a retired Israeli general, said that without a foothold inside Gaza, Israel's security services have come to rely increasingly on technological means to gain intelligence. He said militants in Gaza have found ways to evade that technological intelligence gathering, giving Israel an incomplete picture of their intentions.

“The other side learned to deal with our technological dominance and they stopped using technology that could expose it,” said Avivi, who served as a conduit for intelligence materials under a former military chief of staff.

“They've gone back to the Stone Age,” he said, explaining that militants weren't using phones or computers and were conducting their sensitive business in rooms specially guarded from technological espionage or going underground.

An Egyptian intelligence official said Egypt, which often serves as a mediator between Israel and Hamas, had spoken repeatedly with the Israelis about “something big,” without elaborating.

He said Israeli officials were focused on the West Bank and played down the threat from Gaza. Netanyahu's government is made up of supporters of Jewish West Bank settlers who have demanded a security crackdown in the face of a rising tide of violence there over the last 18 months.

“We have warned them an explosion of the situation is coming, and very soon, and it would be big. But they underestimated such warnings,” said the official, who spoke on condition of anonymity because he wasn't authorized to discuss the content of sensitive intelligence discussions with the media.