Hamas gunmen surged into Israel in a highly organized and meticulously planned operation that suggested a deep understanding of Israel’s weaknesses.

The 10 gunmen from Gaza knew exactly how to find the Israeli intelligence hub — and how to get inside.

After crossing into Israel, they headed east on five motorcycles, two gunmen on each vehicle, shooting at passing civilian cars as they pressed forward.

Ten miles later, they veered off the road into a stretch of woodland, dismounting outside an unmanned gate to a military base. They blew open the barrier with a small explosive charge, entered the base and paused to take a group selfie. Then they shot dead an unarmed Israeli soldier dressed in a T-shirt.

For a moment, the attackers appeared uncertain about where to go next. Then one of them pulled something from his pocket: a color-coded map of the complex.

Reoriented, they found an unlocked door to a fortified building. Once inside, they entered a room filled with computers — the military intelligence hub. Under a bed in the room, they found two soldiers taking shelter.

This sequence was captured on a camera mounted on the head of a gunman who was later killed. The New York Times reviewed the footage, then verified the events by interviewing Israeli officials and checking Israeli military video of the attack as well.

The Hamas commander reviewing a map of the base that includes the intelligence hub.

They provide chilling details of how Hamas, the militia that controls the Gaza Strip, managed to surprise and outmaneuver the most powerful military in the Middle East last Saturday — storming across the border, overrunning more than 30 square miles, taking more than 150 hostages and killing more than 1,300 people in the deadliest day for Israel in its 75-year history.

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, 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. On motorcycles and in pickup trucks, the assailants surged into Israel, overwhelming at least eight military bases and waging terrorist attacks against civilians in more than 15 villages and cities.

Palestinians break into the Israeli side of the Israel-Gaza border fence after gunmen infiltrated areas of southern Israel on Saturday.

Dead people strewn across a road in the Sderot area of Israel, following a mass incursion by Hamas gunmen.

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

The Israeli military says that, once the war is over, it will investigate how Hamas managed to breach its defenses so easily.

But whether the armed forces were careless with their secrets or infiltrated by spies, the revelations have already unnerved officials and analysts who have questioned how the Israeli military — renowned for its intelligence gathering — could have inadvertently revealed so much information about its own operations.

Soldiers from an Israeli military counterterrorism unit battling Hamas in the intelligence hub.

The outcome was a staggering series of atrocities and massacres, in what the Israeli president, Isaac Herzog, has described as the worst mass killing of Jews in a single day since the Holocaust.

It shattered Israel’s aura of invincibility and provoked an Israeli counterattack on Gaza that has killed more than 1,900 Palestinians in a week, the ferocity of which has never been seen in Gaza.

It also upended assumptions that Hamas, long designated a terrorist group by Israel and many Western nations, had gradually become more interested in running Gaza than in using it to launch major assaults on Israel.

Hamas made Israelis think it was “busy with governing Gaza,” said Ali Barakeh, a Hamas leader, in a television interview on Monday. “All the while, under the table, Hamas was preparing for this big attack,” he added.

Hamas In the Kibbutz!’

The terrorists were inside Addi Cherry’s home, on the other side of an unlocked door.

Ms. Cherry, her husband and their three children were hiding inside their eldest son’s bedroom, listening to the gunmen wander around their living room.

“Please help us,” Ms. Cherry texted a friend, as one of the assailants walked closer and closer to the bedroom door.

Then he gripped the door handle.

The Cherry family’s day had begun with a burst of rockets from Gaza, not long after 6 a.m.

Ms. Cherry, an economist, and her husband, Oren, an engineer, rushed with their children into their eldest son’s bedroom, which doubled as a bomb shelter.

Initially, the events of the morning felt distressingly familiar. The Cherry family lives in Kibbutz Nahal Oz, a rural village of some 500 residents, a few hundred yards east of the border with Gaza. Early morning rocket fire — and the ensuing rush to the safe room — is a frequent feature of life in the region.

“Like always,” Ms. Cherry remembered thinking.

But this morning soon felt different. The rockets kept coming, many of them headed deep into Israeli territory.

Interior of a house at the Be’eri kibbutz that was overrun by Hamas militants.

Evgenia Simanovich runs to the reinforced concrete shelter in her home in Ashkelon, Israel, moments after a rocket siren sounded.Credit...Tamir Kalifa for The New York Times

Then, from the fields around the village, came the sound of gunshots.

Mr. Cherry left the bedroom, and peeked through the shutters on their living room windows.

“Oh God,” Ms. Cherry remembered her husband shouting. “Hamas in the kibbutz! Hamas in the kibbutz!”

It was 7:20 a.m.

Hundreds of Hamas invaders, carrying guns, shoulder-borne rocket launchers and wearing the group’s green headband, were streaming through the village fields.

It was part of a coordinated assault that, documents and video show, assigned squads of assailants to precise targets. As some swept through military bases, others charged into residential areas, ruthlessly kidnapping and killing civilians.

Map locating four Israeli kibbutzes: Kfar Aza, Nahal Oz, Be’eri, and Reim, east of the Gaza Strip. It also locates the city of Ashkelon north of the Gaza Strip.