Tunnel warfare with Hamas: past, present, future

Prof. Daphné Richemond-Barak talks with the ‘Post’ about tunnel combat and how nations fight it.

US AMBASSADOR to the United Nations Nikki Haley and Israel’s UN envoy Danny Danon, tour a tunnel in June, excavated by Hamas near the Israeli-Gaza border. (photo credit: MATTY STERN/COURTESY OF U.S. EMBASSY TEL AVIV/VIA REUTERS)
US AMBASSADOR to the United Nations Nikki Haley and Israel’s UN envoy Danny Danon, tour a tunnel in June, excavated by Hamas near the Israeli-Gaza border.
Daphné Richemond-Barak, a legal expert on warfare, begs to differ with those pundits who say the IDF is on the way to having the Gaza tunnel threat licked.
Three weeks ago, the IDF located and destroyed a Hamas attack tunnel near the Gaza border, and it had successfully done the same only about a month before with an Islamic Jihad tunnel.
Richemond-Barak a law of war professor at IDC Herzliya's International Institute for Counter-Terrorism, tells The Jerusalem Post that the IDF’s indisputable progress can be more accurately summarized as “From nothing to being in the game,” as opposed to, “From nothing to case closed.”
The Post was given an exclusive first look at Richemond- Barak’s forthcoming book, Underground Warfare, in which she wades deeply into the strategic and tactical implications of tunnels for modern combat, in addition to the legal considerations involved.
The “nothing” part, she refers to in the interview, comes from how unprepared all experts agree the IDF was for the tunnel threat during the 2014 Gaza war (Operation Protective Edge) in which Hamas successfully used them multiple times for ambushes.
The debate is about whether the IDF’s recent tactical successes and its combination above-and-below ground wall along the Gaza border – due to be finished in 2019 at a cost of NIS 4 billion – are enough to say the army has the threat beaten, or whether the IDF has merely caught up with Hamas, and a game of underground chess is about to begin, she says.
Part of what is astonishing about the book is its comprehensive survey of how widely used tunnel warfare has been through history, the myriad ways it has been used, and how resilient tunnel fighters have morphed their tactics.
From the ancient Jewish King Hezekiah and the ancient Greeks to the US Civil War and World War I, from Vietnam to Hamas in Gaza and ISIS in Syria and Iraq, tunnels have been used throughout the annals of warfare, for both clever defensive and terrifying offensive purposes. The book addresses diverse tunnel threats globally far beyond the Israeli context. Obviously in the Israeli context the focus is on Hamas and Hezbollah.
Hamas has not yet pulled off the threat that former IDF chief of staff Lt.-Gen. Benny Gantz once warned of: Placing explosives under and blowing up an Israeli kindergarten. But the book mentions how the British managed to kill 10,000 German soldiers in one fell swoop with just such an explosives-tunneling attack in 1917 and others having succeeded with the same tactic. That means Gantz’s warning, which Richemond-Barak seconded, still needs to be taken seriously.
BEFORE DISCUSSING whether the IDF has the tunnel threat beaten or has merely developed initial counter-tactics, we need to explain the army’s journey in finding counter-tunnel tactics, what tactics it now employs, and why.
It took years for the IDF to come up with solutions after the tunnel disasters of the 2014 war. Why? Richemond- Barak said that “it was very possible that part of the delay was from the endless options. A lot of people came forward with ‘the’ solution, and there may be have been a lack of understanding that no one could provide a single solution to the problem.
“Once you need to assess multiple options, you may take your time to figure out what is worth investing in, especially when tomorrow you may face different challenges,” she says.
The IDF has only publicized a minimal part of how it is combating tunnels. It has published a number of stories about a range of robots, such as the I-robot, and specially trained dogs for entering and mapping tunnels, tactics usually employed only after a tunnel has been detected.
The IDF has publicized details of a wall under construction along the Gaza border – that it will be 6 meters high and several dozen meters deep – and surrounded by a system designed to locate and measure tunnels using sensors, aerostats and other intelligence gathering methods. Some of the sensors will be attached to large iron cages containing water-resistant pipes.
Richemond-Barak believes some of the sensors were designed to detect movement and noise.
Yet, there are tactics to fool virtually every sensor, and in a sense all of this is a static defensive shield, more than it is a dynamic proactive method for detecting tunnels.
Hamas has found ways in the past to break through a smaller underground wall built by Egypt.
However sophisticated, Israel’s wall and sensors present a static target that can be probed for weaknesses and circumvented.
The Post asked former National Security Council chief and major-general Yaakov Amidror if Hamas could resort to digging its tunnels even deeper than the presumed around 30 meters depth of most of its current tunnels.
Amidror, a fellow at the Jerusalem Institute for Strategic Studies, said digging deeper would be problematic for Hamas in the Gaza terrain, since the area is close to the coast, and at a certain depth, tunnel-diggers would run into water. But he did agree that even with all of the IDF’s progress, Hamas would adapt, and that the army would need to continue to update and adapt its tactics for combating the tunnel threat.
So how to proactively detect and combat tunnels?
Richemond-Barak gives a dizzying list of options that have been used or are being explored by one country or another for detecting, monitoring and destroying tunnels. Israel may sometimes not invest enough resources for this endeavor, she says.
Fascinating options that the IDF either may not use or provide only a limited answer are: magnetometers, electromagnetic induction, electrical resistivity, thermal imagery, and gravity sensors. Most of these methods can yield false positives, have issues with Israeli terrain or must be supplemented with additional measures.
Richemond-Barak did not want to recommend any one option as she believes the answer to combating tunnel warfare is employing a range of technologies, monitoring, intelligence and doctrine.
She points out how differences in terrain between where the IDF confronts Hamas in the south and Hezbollah in the north will likely require the military to employ very different tactics to combat tunnels on these two fronts.
She has a general menu of recommendations.
For detection and monitoring, which include the process of finding, mapping tunnels and staying on top of tunnels after only discovering portions of them, she favors ground-penetrating radar and satellite imaging.
To help with the detection and monitoring process and as defensive measures to prevent Hamas from tunneling into Israeli territory, she supports the IDF’s buffer zones and underground barriers.
Regarding the Gaza-Hamas front, Richemond-Barak said, “ground penetrating radar could be... promising... I think it is being used... maybe recently to find more of the tunnels” by the IDF.
The radar works by “finding voids in the subsurface” of an area, voids that can then be inspected by soldiers, robots or animals to see if the voids represent tunnels.
Already back in 2006, Dan Blumberg of Ben-Gurion University of the Negev in Beersheba used microwave subsurface remote sensing to detect the presence of water in desert soil by looking for the same kinds of voids.
But there are limits to ground penetrating radar. Its effectiveness can be hampered at a certain depth of tunnel, by different kinds of soil, by false positives from water deposits, and by the fact that using it without first narrowing the focus area is “like looking for a needle in a haystack,” she says. She adds that it could not be used on the northern terrain against Hezbollah.
Another method of monitoring she favors is satellite imaging. “If you are keeping records of images of how an area has looked and suddenly you have a slight increase in the height of the surface or a hill, this can help raise questions,” Richemond-Barak says.
Focusing on a specific area can make all of the other potential detection methods more likely to succeed. It is critical to properly train even lower-ranked soldiers viewing the images and of patrols on the ground on what signs to look for. Human intelligence for narrowing the focus-area of tunnel detection remains critical as well. The book mentions a list of nine signs that US tunnel-detectors were trained to look for in Vietnam.
Imaging also has the benefit of being able to follow a suspicious area after warning lights have gone off, even if a tunnel is not yet detected or only portions have been detected.
WHAT ABOUT destroying the tunnels once the IDF finds them? In the 2014 war the IDF realized that air strikes had only limited effectiveness in destroying tunnels.
In addition, they provided no opportunity to obtain intelligence from the tunnels before they were destroyed.
So air strikes are mostly out. Non-democracies have sometimes used toxic gas, flamethrowers or flooding to destroy and clear tunnels, but an army that complies with international law like the IDF cannot really use these tactics or they at least have drawbacks for legitimacy, said Richemond- Barak.
Thermobaric weapons – laser-guided powerful bombs with a delayed fuse that ignites particles with high levels of heat over a period of time, allowing a wider destructive impact on fighters within a tunnel or cave, were used by the US in Afghanistan-Pakistan against Osama bin Laden’s forces. But they are less useful in Gaza terrain and their destructive force rules out their use in the urban Gaza context.
South Korea has used random drilling against North Korean tunnels and we know that Israel is using drilling as part of installing its underground barrier. But random drilling takes too long and requires too many resources to be an effective long-term strategy.
The IDF appears to be relying on liquid explosives, other controlled explosives, and cement -which requires high levels of expertise and quick manipulation before the cement hardens. These tactics can be effective once tunnels are detected and reduce the risk to the soldiers near the tunnels. Smoking out tunnel fighters is another low cost option that Richemond-Barak discusses.
All of these tactics would need to be adjusted if applied to the noisier and more dynamic urban Gaza context, as opposed to just on the deserted border, for detecting attack tunnels.
Even this long list of new tactics does not mean that the IDF has finished off the tunnel threat on any front, she says.
“As we adapted [over] the last three years, we should not kid ourselves. The other side is adapting. Tunnels are very versatile. You can do many things with tunnels. Even during Operation Protective Edge, Hamas came up with innovative ways to use tunnels that they had not done before.”
She adds that the IDF will need to react and adapt to new Hamas tactics, but that there is a built-in delay to the IDF’s ability to do so, since “we can’t see their adjustments. And sometimes even if we know where a tunnel is, we don’t know what they are planning to do.”
Richemond-Barak notes that ISIS tunnel fighters in Syria and Iraq have admitted they had learned from Hamas’s tactics and started to use tunnels more often. However, she says, “now the Syrian theater could influence and trickle down to Hamas,” including explosive tunnel mining and other tactics that ISIS came up with on its own.
In other words, Israel has caught up with Hamas’s last-war tunnel tactics. But as in any arena of warfare, it will need to adjust to any next-war tactics that Hamas or Hezbollah throw at it.