DOHA, Qatar >> Thousands have been killed in the Gaza Strip, with entire families wiped out. Israeli airstrikes have reduced Palestinian neighborhoods to expanses of rubble, while doctors treat screaming children in darkened hospitals with no anesthesia. Across the Middle East, fear has spread over the possible outbreak of a broader regional war.

But in the bloody arithmetic of Hamas’ leaders, the carnage is not the regrettable outcome of a big miscalculation. Quite the opposite, they say: It is the necessary cost of a great accomplishment — the shattering of the status quo and the opening of a new, more volatile chapter in their fight against Israel.

It was necessary to “change the entire equation and not just have a clash,” Khalil al-Hayya, a member of Hamas’ top leadership body, told The New York Times in Doha. “We succeeded in putting the Palestinian issue back on the table, and now no one in the region is experiencing calm.”

Since the shocking Hamas attack on Oct. 7, in which Israel says about 1,400 people were killed — most of them civilians — and more than 240 others dragged back to Gaza as captives, the group’s leaders have praised the operation, with some hoping it will set off a sustained conflict that ends any pretense of coexistence among Israel, Gaza and the countries around them.

“I hope that the state of war with Israel will become permanent on all the borders, and that the Arab world will stand with us,” Taher Nounou, a Hamas media adviser, told the Times.

In weeks of interviews, Hamas leaders, along with Arab, Israeli and Western officials who track the group, said the attack had been planned and executed by a tight circle of commanders in Gaza who did not share the details with their own political representatives abroad or with their regional allies like Hezbollah, leaving people outside the enclave surprised by the ferocity, scale and reach of the assault.

The attack ended up being broader and more deadly than even its planners had anticipated, they said, largely because the assailants managed to break through Israel’s vaunted defenses with ease, allowing them to overrun military bases and residential areas with little resistance. As Hamas stormed through a swath of southern Israel, it killed and captured more soldiers and civilians than it expected to, officials said.

The assault was so devastating that it served one of the plotters’ main objectives: It broke a long-standing tension within Hamas about the group’s identity and purpose. Was it mainly a governing body — responsible for managing day-to-day life in the blockaded Gaza Strip — or was it still fundamentally an armed force, unrelentingly committed to destroying Israel and replacing it with an Islamist Palestinian state?

With the attack, the group’s leaders in Gaza — including Yehia Sinwar, who had spent more than 20 years in Israeli prisons, and Mohammed Deif, a shadowy military commander whom Israel had repeatedly tried to assassinate — answered that question. They doubled down on military confrontation.

The weeks since have seen a furious Israeli response that has killed more than 10,000 people in Gaza, according to health officials there. But for Hamas, the attack stemmed from a growing sense that the Palestinian cause was being pushed aside, and that only drastic action could revive it.

On the surface, the months before the brutal assault seemed relatively quiet in Gaza. Hamas had sat out recent clashes between Israel and other militants, and the group’s political leaders were 1,000 miles away in Qatar, negotiating to get more aid and jobs for residents of the impoverished territory.

But the frustration was building. Hamas leaders in Gaza were flooded with images of Israeli settlers attacking Palestinians in the West Bank, Jews openly praying at a contested site customarily reserved for Muslims, and Israeli police storming Al-Aqsa Mosque in Jerusalem, a touchstone for Palestinian claims to the holy city. The prospect of Israel’s normalizing ties with Saudi Arabia, long a deep-pocketed patron of the Palestinian cause, appeared closer than ever.

Then, on a quiet Saturday morning, Hamas attacked.

It was clear in advance that Israel would respond by bombarding Gaza, killing Palestinian civilians.

“What could change the equation was a great act, and without a doubt, it was known that the reaction to this great act would be big,” al-Hayya said.

But, he added, “We had to tell people that the Palestinian cause would not die.”

Some Israeli officials now express deep regret that they so profoundly misjudged Sinwar and his intentions, one of many security failures that allowed Hamas to pour through the border fence and rampage, largely unimpeded, for hours.

“I will carry the burden of this mistake for the rest of my life,” said one Israeli official.

A New Leader in Gaza

Sinwar took the helm of Hamas in Gaza in 2017. A tough, unsmiling man with closely cropped white hair and a trim beard, he hailed from the first generation of Hamas, an armed group founded during the first Palestinian intifada, or uprising, in the late 1980s and ultimately classified as a terrorist organization by the United States and many other nations.

Sinwar helped create the Qassam Brigades, Hamas’ armed wing, which became notorious for dispatching suicide bombers to Israeli cities and firing rockets from Gaza at Israeli towns. He also policed Hamas for suspected spies recruited by Israel, developing a reputation for such brutality toward them that he earned the nickname “the butcher of Khan Younis,” from the Gazan town of his birth.

In 1988, he was detained and later prosecuted for the killing of four Palestinians suspected of collaborating with Israel, according to Israeli court records. He ended up in prison in Israel for more than two decades, an experience he called educational.

“They wanted the prison to be a grave for us. A mill to grind our will, determination and bodies,” he said in 2011. “But, thank God, with our belief in our cause, we turned the prison into sanctuaries of worship and academies for study.”

Much of that education was studying his enemy.

He learned Hebrew, giving him a deeper understanding of Israeli society, and he developed a dedication to freeing the thousands of Palestinian prisoners in Israel. Israel has convicted many of them of violent crimes; Palestinians widely consider them to be held unjustly.

In 2011, Sinwar was released in a prisoner swap that Hamas took as a signature lesson: Israel was willing to pay a high price for its captives.

Hamas traded a single Israeli soldier, Gilad Shalit, for more than 1,000 Palestinians, including Sinwar, a prison leader who had been involved in the negotiations. Freeing him was a big prize for Hamas, and he vowed to release more inmates.

“For me, it is a moral obligation,” he said in a 2018 interview. “I will try more than my best to free those who are still inside.”

When Sinwar returned to Gaza in 2011, the Palestinian movement was deeply divided.

Some factions had signed accords with Israel, meant to pave the way for a two-state solution. The Palestinian Authority, envisioned as a Palestinian government in waiting, had limited authority over parts of the West Bank and remained officially committed to negotiating an end to the conflict.

Hamas, meanwhile, effectively sought to undo history, starting with 1948, when more than 700,000 Palestinians fled or were expelled from their homes in what would become Israel during the war surrounding the foundation of the Jewish state.

For Hamas, that displacement, along with Israel’s occupation of the West Bank and Gaza during the 1967 Mideast war, were great historical wrongs that had to be righted by force of arms. Hamas dismissed peace talks with Israel as a betrayal, viewing them as a capitulation to Israel’s control over what the group considered occupied Palestinian land.

The Palestinian political rift became etched into geography in 2007, when Hamas won a bout of factional fighting in Gaza and took charge of the territory. Suddenly, it was not just fighting Israel, but also governing Gaza. Israel, in tandem with Egypt, imposed a blockade on the strip aimed at weakening Hamas, plunging Palestinians in Gaza into deepening isolation and poverty.

By the time Sinwar returned to Gaza, Hamas was already entrenched as the de facto government and had settled into what Tareq Baconi, a Hamas expert, has called a “violent equilibrium” with Israel. Deep hostility frequently erupted into deadly exchanges of Hamas rockets and Israeli airstrikes. But most of Gaza’s commercial goods and electricity came from Israel, and Hamas often sought to loosen the blockade during cease-fire talks.

Hamas leaders were ambivalent about the group’s new governing role, with some believing they needed to improve life for Palestinians in Gaza, and others considering governance a distraction from their original, military mission, experts say. Hamas derided the Palestinian Authority for its cooperation with Israel, including the use of Palestinian police to prevent attacks on Israel. Some Hamas leaders feared that their own group, in negotiating daily life issues with Israel, was, in a lesser way, on the same path.

In 2012, Sinwar became the armed wing’s representative to Hamas’ political leadership, linking him more tightly to the leaders of the military wing, including Deif, the mysterious head of the Qassam Brigades. The two men were key architects of the Oct. 7 attack, according to Arab and Israeli officials.

When Sinwar became the overall head of Hamas in Gaza in 2017, he sometimes projected an interest in accommodation with Israel. In 2018, he gave a rare interview to an Italian journalist working for an Israeli newspaper and appealed for a cease-fire to ease the suffering in Gaza.

“I am not saying I won’t fight anymore,” he said. “I am saying that I don’t want war anymore. I want the end of the siege. You walk to the beach at sunset and you see all these teenagers on the shore chatting and wondering what the world looks like across the sea. What life looks like,” he added. “I want them free.”

Hamas also issued a political program in 2017 that allowed for the possibility of a two-state solution, while still not recognizing Israel’s right to exist.

Israel granted some concessions, agreeing in 2018 to allow $30 million a month in aid from Qatar into Gaza and increasing the number of permits for Palestinians in Gaza to work inside Israel, bringing much needed cash into Gaza’s economy.

Violence continued to break out. In 2021, Hamas launched a war to protest Israeli efforts to evict Palestinians from their homes in east Jerusalem and Israeli police raids of Al-Aqsa Mosque in Jerusalem’s Old City.

That was a turning point, Osama Hamdan, a Hamas leader based in Beirut, told the Times. Instead of firing rockets over issues in Gaza, Hamas was fighting for concerns central to all Palestinians, including those outside the enclave. The events also convinced many in Hamas that Israel sought to push the conflict past a point of no return that would ensure the impossibility of Palestinian statehood.

“The Israelis were only concerned with one thing: How do I get rid of the Palestinian cause?” Hamdan said. “They were heading in that direction and not even thinking about the Palestinians. And if the Palestinians did not resist, all of that could have taken place.”

Building Capabilities

Still, in 2021, Israeli military intelligence and the National Security Council thought that Hamas wanted to avoid another war, according to people familiar with the assessments.

Hamas, too, bolstered the idea that it was prioritizing governing over battle. Twice, the group refrained from joining clashes with Israel started by Palestinian Islamic Jihad, a smaller militia in Gaza. Hamas’ political leaders were trying through mediators in Qatar to increase the aid going into Gaza and the number of laborers going out to work in Israel, according to diplomats involved in the discussions.

Many in Israel’s security establishment also came to believe that its complex border defenses to shoot down rockets and prevent infiltrations from Gaza were enough to keep Hamas contained.

But inside Gaza, Hamas’ capabilities grew.

By Oct. 7, Hamas was estimated to have 20,000 to 40,000 fighters, with about 15,000 rockets, mainly manufactured in Gaza with components most likely smuggled in through Egypt, according to American and other Western analysts. The group had mortars, anti-tank missiles and portable air-defense systems as well, they said.

Sinwar had also restored the group’s ties to its longtime backer, Iran, which had frayed in 2012, when Hamas shuttered its office in Syria, a close Iranian ally, amid Syria’s civil war.

That restoration deepened the relationship between Hamas’ military wing in Gaza and the so-called axis of resistance, Iran’s network of regional militias, according to regional diplomats and security officials. In recent years, a stream of Hamas operatives traveled from Gaza to Iran and Lebanon for training by the Iranians or Hezbollah, adding a layer of sophistication to Hamas’ capabilities, the officials said.

That training, however, did not mean that Iran or Hamas’ other regional allies knew how or when those capabilities might be used, the officials said.

For all of Hamas’ covert preparations, the group itself had advertised some of the most effective weapons it deployed on Oct. 7. After the assault began, the group released training footage of its fighters paragliding in Gaza well before the attack, an activity easy for Israel to see, and of Hamas fighters training to take hostages from a mock-up Israeli town in Gaza.

In May 2021, Hamas released three statements about its new drones. One included a video of masked fighters launching guided kamikaze drones. Another included aerial surveillance footage of communications towers inside Israel and Israeli tanks.

An article published on the military wing’s Arabic website boasted: “The enemy’s aircraft no longer monopolize the sky of Palestine.”

On Oct. 7, Hamas used paragliders to fly over the border fence and exploding drones to disable Israel’s border security architecture. The attackers who then stormed Israeli bases and communities carried maps, most likely fleshed out in part by Palestinian workers Hamas had recruited as spies, one regional security official said.

One of the big mistakes Israel made, Arab and Israeli officials say, was failing to grasp the way Hamas would combine relatively simple tools into a sophisticated, multipronged attack that outmaneuvered a much larger, more powerful army.

Motivation to Strike

While building the capabilities for the assault took years, the decision to launch it on Oct. 7 was a secret closely guarded by a small number of Hamas leaders in Gaza who did not even inform those taking part until the last minute to prevent interception by regional intelligence services, according to Hamas and regional officials.

A key objective was to take as many Israeli soldiers captive as possible for use in a prisoner swap, according to two Arab officials whose governments talk to Hamas.

One regional security official said Hamas had expected that, once the attack began, Palestinians elsewhere would rise up against Israel, other Arab populations would explode against their governments and the group’s regional allies, including Hezbollah, would join the fight.

But at least four intelligence services — two Arab and two European — have assessed that Hezbollah had no advance knowledge of the attack, according to officials with access to intelligence reports.

Hamas’ own political leaders outside Gaza were also surprised by the assault, according to several Arab and Western officials who track their movements. They have, nonetheless, praised it for reinvigorating the armed struggle against Israel.

“Hamas’ goal is not to run Gaza and to bring it water and electricity and such,” said al-Hayya, the politburo member. “Hamas, the Qassam and the resistance woke the world up from its deep sleep and showed that this issue must remain on the table.”

“This battle was not because we wanted fuel or laborers,” he added. “It did not seek to improve the situation in Gaza. This battle is to completely overthrow the situation.”

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This article originally appeared in The New York Times.