By Maria Abi Habib and Sheera Frenkel

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

For years, analysts have pointed to underground smuggling routes to explain how Hamas stayed 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 weaponry out of the thousands of munitions that failed to detonate when Israel lobbed them into Gaza, according to weapons experts and Israeli and Western intelligence officials. Hamas is also arming its fighters with weapons stolen from Israeli military bases.

Intelligence gathered during months of fighting revealed that, just as Israeli authorities misjudged Hamas’ intentions before Oct. 7, they also underestimated its ability to obtain arms.

What is clear now is that the very weapons that Israeli forces have used to enforce a blockade of Gaza over the past 17 years are now being used against them. Israeli and American military explosives have enabled Hamas to shower Israel with rockets and, for the first time, penetrate Israeli towns from Gaza.

“Unexploded ordnance is a main source of explosives for Hamas,” said Michael Cardash, the former deputy head of the Israeli National Police Bomb Disposal Division and an Israeli police consultant. “They are cutting open bombs from Israel, artillery bombs from Israel, and a lot of them are being used, of course, and repurposed for their explosives and rockets.”

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

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

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 scope has startled weapons experts and diplomats alike.

Israeli authorities also knew that their armouries were vulnerable to theft. A military report from 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 made their way to the West Bank, and others to Gaza by way of Sinai. However the report focused on military security. The consequences were treated almost as an afterthought: “We are fuelling our enemies with our own weapons,” read one line of the report, which was viewed by The New York Times.

The consequences became apparent on Oct. 7. Hours after Hamas breached the border, four Israeli soldiers discovered the body of a Hamas gunman who was killed outside the Re’im military base. Hebrew writing was visible on a grenade on his belt, said one of the soldiers, who recognized it as a bulletproof Israeli grenade, a recent model. Other Hamas fighters overran the base, and Israeli military officials say some weapons were looted and returned to Gaza.

A few miles away, members of an Israeli forensic team collected one of the 5,000 rockets fired by Hamas that day. Examining the rocket, they discovered that its military-grade explosives had most likely come from an unexploded Israeli missile fired into Gaza during a previous war, according to an Israeli intelligence officer.

The Oct. 7 attacks showcased the patchwork arsenal that Hamas had stitched together. It included Iranian-made attack drones and North Korean-made rocket launchers, the types 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, like anti-tank explosives, rocket-propelled grenade warheads, thermobaric grenades and improvised devices were repurposed Israeli arms, according to Hamas videos and remnants uncovered by Israel.

Rockets and missiles require huge quantities of explosive material, which officials say is the most difficult item to smuggle into Gaza.

Yet Hamas fired so many rockets and missiles on Oct. 7 that Israel’s Iron Dome air defence system could not keep up. Rockets struck towns, cities and military bases, giving cover to the militants who stormed 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 a crackdown on smuggling tunnels leading into and out of Gaza forced Hamas to get creative.

Its manufacturing abilities are now sophisticated enough to saw into the warheads of bombs weighing up to 2,000 pounds, to harvest the explosives and to repurpose them.

“They have a military industry in Gaza. Some of it is above ground, some of it is below ground, and they are able to manufacture a lot of what they need,” said Eyal Hulata, who served as Israel’s national security adviser and head of its National Security Council before stepping down early last year.

One Western military official said that most of the explosives that Hamas is using in its war with Israel appear to have been manufactured using unexploded Israeli-launched munitions. One example, the official said, was an explosive booby trap that killed 10 Israeli soldiers in December.

The military wing of Hamas, the Qassam Brigades, has flaunted its manufacturing abilities for years. After a war in 2014 with Israel, it established engineering teams to collect unexploded munitions like howitzer rounds and American-made MK-84 bombs.

These teams work with the police’s explosive ordnance-disposal units, allowing people to safely return to their homes. They also help Hamas gear up for the next war.

“Our strategy aimed to repurpose these pieces, turning 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 were doing: sawing into warheads, scooping out explosive material — usually a powder — and melting it down to reuse.

In 2019, Qassam commandos discovered hundreds of munitions on two World War I-era British military vessels that had sunk off the coast of Gaza a century earlier. The discovery, Qassam boasted, allowed it to make hundreds of new rockets.

Early in the current war, a Qassam video showed militants assembling Yassin 105 rockets in a sunless manufacturing facility.

“The most essential way for Hamas to obtain weaponry is through domestic manufacture,” said Ahmed Fouad Alkhatib, a Middle East policy analyst who grew up in Gaza. “It’s just a tweak of chemistry and you can make pretty much whatever you want.”

Israel restricts the mass importation of construction materials that can be used to build rockets and other weapons. But each new round of fighting leaves behind neighbourhoods of rubble from which militants can pluck pipes, concrete and other valuable materials, Alkhatib said.

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

According to two Israeli intelligence officials, at least a dozen small tunnels were still running between Gaza and Egypt before Oct. 7. A spokesperson for the Egyptian government said its military had done its part to shut down tunnels on its side of the border. “Many of the weapons currently inside the Gaza Strip are the result of smuggling from within Israel,” the spokesperson said in an email.

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

Israel estimates that it has conducted at least 22,000 strikes on Gaza since Oct. 7. Each often involves multiple rounds, meaning tens of thousands of munitions have likely been dropped or fired — and thousands failed to detonate.

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

-New York Times