Less than a month before Hamas terrorists blew through Israel’s high-tech “Iron Wall” and launched an attack that would leave more than 1,200 Israelis dead, they practiced in a very public dress rehearsal.

A two-minute propaganda video posted to social media by Hamas on Sept. 12 shows fighters using explosives to blast through a replica of the border gate, sweep in on pickup trucks and then move building by building through a full-scale reconstruction of an Israeli town, firing automatic weapons at human-silhouetted paper targets.

The Islamic terrorist group’s live-fire exercise dubbed operation “Strong Pillar” also had terrorists in body armor and combat fatigues carrying out operations that included the destruction of mock-ups of the wall’s concrete towers and a communications antenna, just as they would actually do in the deadly attack Oct. 7.

With meticulous planning and extraordinary awareness of Israel’s secrets and weaknesses, Hamas and its allies overwhelmed the length of Israel’s front with Gaza shortly after dawn Oct. 7, shocking a nation that has long taken the superiority of its military as an article of faith.

Using drones, Hamas destroyed key surveillance and communications towers along the border with Gaza, imposing vast blind spots on the Israeli military. With explosives and tractors, Hamas blew open gaps in the border barricades, allowing 200 attackers to pour through in the first wave and another 1,800 later that day, officials say.

Hamas planning documents, videos of the assault and interviews with security officials show that the terrorists had a sophisticated understanding of how the Israeli military operated, where it stationed units, and even the time it would take for reinforcements to arrive.

While Israel’s security and intelligence services were caught flatfooted by Hamas’ ability to breach its defenses, the group appears to have hidden its extensive preparations for the assault in plain sight.

One of the compounds Hamas used to prepare was so close to an Israeli border checkpoint that soldiers would have been able to observe the site with binoculars.

“There clearly were warnings and indications that should have been picked up,” said Bradley Bowman, a former U.S. Army officer who is now senior director of the Center on Military and Political Power at the Foundation for Defense of Democracies, a Washington research institute. “Or maybe they were picked up, but they didn’t spark necessary preparations to prevent these horrific terrorist acts from happening.”

Bowman said there are indications that Hamas intentionally led Israeli officials to believe it was preparing to carry out raids in the West Bank, rather than Gaza. It was also potentially significant that the exercise has been held annually since 2020 in December, but was moved up by nearly four months this year to coincide with the anniversary of Israel’s 2005 withdrawal from Gaza.

Michael Milshtein, a retired Israeli colonel who previously led the military intelligence department overseeing the Palestinian territories, said he was aware of the Hamas videos, but was still caught off guard by the scale of the Oct. 7 attack.

“We knew about the drones, we knew about booby traps, we knew about cyberattacks and the marine forces. The surprise was the coordination between all those systems,” Milshtein said.

The seeds of Israel’s failure to anticipate and stop the attack go back at least a decade.

Faced with recurring attacks from Hamas terrorists tunneling under Israel’s border fence, Prime Minister Benjamin Netanyahu proposed a concrete solution — build a bigger wall.

With financial help from U.S. taxpayers, Israel completed construction of a $1.1 billion project to fortify its existing defenses along its 40-mile land border with Gaza in 2021.

The new, upgraded barrier includes a “smart fence” up to 19.7 feet high, festooned with cameras that can see in the dark, razor wire and seismic sensors capable of detecting the digging of tunnels more than 200 feet below.

Manned guard posts were replaced with concrete towers topped with remote- controlled machine guns.

“In our neighborhood, we need to protect ourselves from wild beasts,” Netanyahu said in 2016, referring to Palestinians and neighboring Arab states.

“At the end of the day as I see it, there will be a fence like this one surrounding Israel in its entirety,” Netanyahu said.

Hamas fighters pushed through Netanyahu’s wall in a matter of minutes.

In the days since the breach, senior Israeli officials have largely deflected questions about the wall and the apparent intelligence failure.

Rear Adm. Daniel Hagari, chief spokesman for the Israel Defense Forces, acknowledged the military owes the public an explanation, but said now is not the time.

“First, we fight, then we investigate,” he said.

The New York Times contributed.