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One of the reasons that Hamas felt emboldened enough to launch a rocket assault on Jerusalem last month – an action that provoked an 11-day intensive armed conflict with Israel – was because of its progress in building up its military-terrorist force.

With Iran's help, Hamas entered this conflict with better rocket building know-how, and some 15,000 rockets of varying ranges. Most were made in Gaza, together with Palestinian Islamic Jihad's 10,000 rockets. The conflict also came with a new battle doctrine designed to try to saturate Israeli air defenses with unprecedented large barrages.

Hamas felt it could push its weight around, and Israeli deterrence experienced an erosion in the days leading up to the conflict.

After identifying violence in Jerusalem as an opportunity to overtake its rival, the Fatah-run Palestinian Authority, and position itself as the authentic "guardian of Jerusalem" and the Al-Aqsa Mosque, Hamas recklessly marched Gaza into a new destructive war, largely because of the improved rocket arsenal that it had spent years building.

Israel had carefully monitored Hamas's efforts to dramatically increase the number of rockets it could fire at once, as well as attempts to fire at lower trajectories to try and confuse the Iron Dome air defense system, which underwent upgrades and was able to cope with the challenge.

And while Israel attempted to disrupt Hamas's force build-up process, most of the work to build new rocket warheads in Gaza, filled with explosives such as C4, TNT, and RDX, went unhindered.

Hamas routinely tore sewer pipes out of the ground to create the rocket engine body, and even used fiberglass, sent to Gaza to repair and improve fishing boats, in its rocket industry.

This is why Israel asked international aid organizations last year to introduce plastic, rather than metal pipes to Gaza.

"They took out the pipes and used them to manufacture rockets, instead of giving their civilians better living conditions," a senior Israeli defense source stated.

"We received many requests to introduce fiberglass for Gazan fishing boats. This is where it went to instead – to the rockets," said the source.

Hamas imported chemicals to make rocket propellant, including castor oil, and used additives such as aluminum dust for propellant. Its weapons engineers even took regular salt, and, using Iranian techniques, converted it into a substance called AP, which is a rocket propellant.

Now, as the Israel-Hamas ceasefire enters its third week, the key question of how it might be possible to prevent Hamas from once again rebuilding its terrorist army arises.

As recent developments have shown, the truce's staying power largely depends on how effectively Hamas can be prevented from rearming quickly.

Hamas already is seeking to exploit the legitimate humanitarian and economic needs of 2 million Gazan civilians, whom it holds hostage to its agenda of running an Islamist terror state.

Hamas would like once again to see Gaza flooded with construction material and cash, which it can then divert to building new rocket factories, new combat tunnels, and to produce other weapons designed to terrorize Israeli civilians.

This means that the ability to keep the Gazan arena stable largely depends on Israel's ability to keep Hamas from rearming.

Even during "Operation Guardian of the Walls," the IDF's 11-day campaign to severely degrade the capabilities of Hamas and PIJ, Hamas's boundless cynicism and willingness to exploit assistance to Gazan civilians was on display.

A senior Israeli security source described how, following a Hamas request for humanitarian aid to enter Gaza during the fighting, Israel opened the Erez border crossing terminal and began sending trucks with aid into the Strip. "They attacked the terminal with mortar shells," the official said.

Prior to the eruption of the conflict, Gaza was bristling with weapons production centers, and this domestic arms industry formed a central target for the Israeli Air Force.

According to IDF sources, a major part of Hamas's weapons research and development and production capabilities has been degraded. This includes an extensive campaign targeting research and development operatives, and the bombing of many weapons workshops where rockets are made and where their warheads, ranges, and accuracy levels are continuously improved.

After the ceasefire took root, President Joe Biden expressed his desire to "provide rapid humanitarian assistance and to marshal international support for the people of Gaza and the reconstruction efforts ... in a manner that does not permit Hamas to simply restock its military arsenal."

History shows that is far easier said than done. And looking ahead, Israeli defense officials are signaling that the reality that existed prior to the conflict cannot be allowed to repeat itself.

After 2014's Operation Protective Edge, the Israeli public was told that a new mechanism to control and monitor the use of cement entering Gaza would prevent its diversion to Hamas's 'metro' network of combat tunnels. But that didn't happen. Those tunnels allowed Hamas personnel and weapons to move around out of the sight of the Israel Air Force (the IAF destroyed some 100 kilometers of such tunnels in Gaza during Operation Guardian of the Walls, according to Israeli assessments).

Since 2014, according to the security source, enough cement and metal entered Gaza to build roughly 20 Burj Khalifa-sized skyscrapers – the Dubai-based tallest building in the world. Most of those materials went underground, to Hamas's tunnel project.

Now, Israel faces a serious dilemma. If it is unable to produce a new and improved inspections mechanism, working with international aid organizations and states that would work to help rebuild Gaza, will it allow cement and metal back into Gaza? Or will residents of destroyed buildings end up living in tents?

"A mechanism can be built to supervise reconstruction materials – but not by Israel by itself," said the source.

The sentiment was echoed Monday by Defense Minister Benny Gantz.

"I spoke with the Americans, the Egyptians, and the representatives of many others in the world, and I made it clear to them that alongside the entry of goods like food and medicines, which are necessary for basic humanitarian sustenance, we will demand that the reconstruction of the Gaza Strip will be accompanied by long-term quiet, and the return of the soldiers," he said. Hamas holds the remains of two IDF soldiers as bargaining chips for the release of Hamas prisoners. Two Israeli citizens are also being held hostage by Hamas.

Gantz also called for the Palestinian Authority to start playing a role in the Gazan reconstruction effort, and has indicted that the era of seeing $30 million in Qatari funds being diverted to Hamas's military wing each month, must now end as well.

According to Maj. Gen. (res) Eitan Dangot, the former Israeli Coordinator of Government Activities in the Territories, Egypt is playing an important role, in mediating attempts to create a new way to supervise goods entering Gaza, and attempting to create a new foothold for the Palestinian Authority in the Gaza Strip.

During a subsequent meeting with the current Israeli Coordinator of Government Activities in the Territories, Maj. Gen. Ghassan Elian, and the UN's Special Envoy to the region, Tor Wennesland, Gantz unveiled a plan by the Israeli defense establishment designed to both enable a rebuilding of Gaza, and to strengthen the role of the Palestinian Authority in Gaza's future, as well as that of moderate Sunni states in the region.

The formula of blindly throwing money and materials into Gaza and hoping for calm has been discredited. Whether it helps Gaza rebuild without arming terrorists remains to be seen.

IPT Senior Fellow Yaakov Lappin is a military and strategic affairs correspondent. He also conducts research and analysis for defense think tanks, and is the military correspondent for JNS. His book, The Virtual Caliphate, explores the online jihadist presence.

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