Where does Hamas get its weapons? Increasingly from Israel.

Israeli military and intelligence officials have concluded that a significant number of weapons used by Hamas in the October 7 attacks and in the Gaza war came from an unlikely source: the Israeli military itself.

For years, analysts have pointed to underground smuggling routes to explain how Hamas remained so heavily armed despite an Israeli military blockade of the Gaza Strip. But recent intelligence has shown the extent to which Hamas has been able to build many of its rockets and anti-tank weapons from the thousands of munitions that failed to detonate when Israel sent them into Gaza, according to weapons experts and Israeli and Western intelligence services. civil servants. Hamas also arms its fighters with weapons stolen from Israeli military bases.

Intelligence gathered during months of fighting showed that just as Israeli authorities misjudged Hamas's intentions before October 7, they also underestimated Hamas's ability to obtain weapons.

What is now clear is that the very weapons that the Israeli forces have used to enforce a blockade of Gaza for the past seventeen years are now being used against them. Israeli and US military explosives have enabled Hamas to shower Israel with rockets and enter Israeli cities from Gaza for the first time.

“Unexploded ordnance is a major source of explosives for Hamas,” said Michael Cardash, former deputy head of Israel's National Police Bomb Disposal Unit and advisor to the Israel Police. “They're cutting open bombs from Israel, artillery bombs from Israel, and a lot of them, of course, are being used and reused for their explosives and missiles.”

Weapons experts say that roughly 10 percent of munitions typically fail to detonate, but in Israel's case the figure could be even higher. Israel's arsenal includes Vietnam-era missiles, long since retired by the United States and other military powers. The failure rate of some of these missiles could be as high as 15 percent, said an Israeli intelligence officer who, like others interviewed for this article, spoke on condition of anonymity to discuss intelligence matters.

Whatever the case, years of sporadic bombing and the recent bombardment of Gaza have left the area littered with thousands of tons of unexploded ordnance waiting to be reused. One 750-pound bomb that fails to detonate can become hundreds of rockets or missiles.

Hamas did not respond to messages seeking comment. The Israeli military said in a statement that it was committed to dismantling Hamas, but did not answer specific questions about the group's weapons.

Israeli officials knew before the October attacks that Hamas could salvage some Israeli-made weapons, but the scale has shocked weapons experts and diplomats alike.

Israeli authorities also knew that their armories were vulnerable to theft. A military report early last year noted that thousands of bullets and hundreds of guns and grenades had been stolen from poorly guarded bases.

From there, the report said, some went to the West Bank, and others went to Gaza via Sinai. But the report focused on military security. The consequences were treated almost as an afterthought: “We fuel our enemies with our own weapons,” said one line from the report, which was viewed by The New York Times.

The consequences became clear on October 7. Hours after Hamas crossed the border, four Israeli soldiers discovered the body of a Hamas gunman killed outside the Re'im military base. A grenade on his belt showed Hebrew writing, said one of the soldiers, who recognized it as a bulletproof Israeli grenade, a recent model. Other Hamas fighters have overrun the base, and Israeli military officials say some weapons have been looted and returned to Gaza.

A few kilometers away, members of an Israeli forensic team collected one of the 5,000 rockets fired by Hamas that day. Upon examining the rocket, they found that the military-grade explosives most likely came from an unexploded Israeli rocket fired into Gaza during a previous war, an Israeli intelligence officer said.

The October 7 attacks exposed the patchwork arsenal that Hamas had stitched together. It included Iranian-made attack drones and North Korean-made rocket launchers, the type of weapons that Hamas is known to smuggle into Gaza through tunnels. Iran remains a major source of Hamas' money and weapons.

But other weapons, such as anti-tank explosives, RPG warheads, thermobaric grenades and improvised devices, were repurposed Israeli weapons, according to Hamas videos and remains discovered by Israel.

Missiles and rockets require huge amounts of explosive material, which officials say is the most difficult item to smuggle into Gaza.

Yet on October 7, Hamas fired so many rockets that Israel's Iron Dome air defense system could not keep up. Rockets struck villages, towns and military bases, providing cover for the militants storming into Israel. One rocket hit a military base believed to house part of Israel's nuclear missile program.

Hamas once relied on materials like fertilizer and powdered sugar — which, pound for pound, are not as powerful as military-grade explosives — to build rockets. But since 2007, Israel has enforced a strict blockade, restricting the import of goods, including electronics and computer equipment, that could be used to make weapons.

That blockade and the crackdown on the smuggling tunnels leading in and out of Gaza forced Hamas to be creative.

Manufacturing capabilities are now advanced enough to cut the warheads of bombs weighing up to 2,000 pounds, collect the explosives and reuse them.

“They have a military industry in Gaza. Some of it is above ground, some of it is below ground, and they can produce a lot of what they need,” said Eyal Hulata, who served as Israel's national security adviser and head of the National Security Council before resigning prematurely. last year.

A Western military official said most of the explosives used by Hamas in its war with Israel appear to be manufactured using unexploded ordnance launched by Israel. One example, the official said, was an explosive booby trap which killed ten Israeli soldiers in December.

Hamas's military wing, the Qassam Brigades, has been showing off its production capabilities for years. After a 2014 war with Israel, it set up technical teams to collect unexploded ordnance such as howitzer bullets and American-made MK-84 bombs.

These teams work with police explosive ordnance disposal units to ensure people can return to their homes safely. They are also helping Hamas prepare for the next war.

“Our strategy was to repurpose these pieces and turn this crisis into an opportunity,” a Qassam Brigades commander told Al Jazeera in 2020.

Qassam's media arm has released videos in recent years showing exactly what they did: cutting into nuclear warheads, extracting explosive material – usually a powder – and melting it down for reuse.

In 2019, Qassam commandos discovered hundreds of munitions on two World War I British military ships that had been sunk off the coast of Gaza a century earlier. The discovery, Qassam boasted, allowed it to create hundreds of new missiles.

At the beginning of the current war, a Qassam video was shown militants assembling Yassin 105 rockets in a sunless production facility.

“The most essential way for Hamas to obtain weapons is through domestic production,” said Ahmed Fouad Alkhatib, a Middle East policy analyst who grew up in Gaza. “It's just a little bit of chemistry and you can make pretty much anything you want.”

Israel restricts mass imports of construction materials that can be used to build missiles and other weapons. But each new round of fighting leaves neighborhoods littered with rubble from which militants can pluck pipes, concrete and other valuable materials, Mr. Alkhatib said.

Hamas cannot manufacture everything. Some things are easier to buy on the black market and smuggle into Gaza. Sinai, the largely uninhabited desert area between Israel, Egypt and the Gaza Strip, remains a center for arms smuggling. According to Israeli intelligence assessments, weapons from conflicts in Libya, Eritrea and Afghanistan have been discovered in Sinai.

At least a dozen small tunnels ran between Gaza and Egypt before October 7, according to two Israeli intelligence officials. An Egyptian government spokesman said the army had done its part by closing tunnels on its side of the border. “Many of the weapons currently in the Gaza Strip are the result of smuggling from Israel,” the spokesperson said in an email.

But the besieged streets of Gaza themselves are increasingly a source of weapons.

Israel estimates it has carried out at least 22,000 attacks on Gaza since October 7. Each attack often involves multiple rounds, meaning tens of thousands of rounds of ammunition were likely dropped or fired – and thousands failed to detonate.

“Artillery, hand grenades, other munitions – tens of thousands of unexploded ordnance will be left behind after this war,” said Charles Birch, head of the UN Mine Action Service in Gaza. These “are like a free gift for Hamas.”

Vivian Yee contributed reporting from Cairo, and Zakaria Zakaria from Rotterdam, Netherlands.