The invasion and massacre in Israel on October 7 brutally showed how Hamas has significantly improved and strengthened its tactical and strategic terror capabilities since it began to dig into and hide in the Gaza Strip decades ago.
The infamous Hamas tunnels have played a central role in this worrisome development. Prof. Joel Roskin, a geomorphologist and geologist at Bar-Ilan University's geography and environment department, has followed the changes in the Gaza tunnels over the years, analyzed the conditions that allowed their formation and expansion and revealed what geological and security conditions have enabled their speedy development.
Three years ago, Roskin published a book chapter based on his study “Underground Warfare in the Gaza Strip and the Military Complexity of Combating It.” A timely article on the same topic and with the same name is currently in the final stages of acceptance by the academic journal Studies in Conflict and Terrorism.
The article, based on his experience as head of the terrain research department in the Southern Command in the 2000s and on information publicized in the media, describes the field data and the geopolitical conditions that literally provided the fertile ground for the development of the tunnels.
Clear records of tunneling operations extend back more than 4,000 years – Assyrian carvings show engineering units belonging to Sargon of Akkad (who reigned between 2,334 and 2,279 BCE) undermining the walls of enemy cities. American troops attacking Al Qaeda positions and pursuing Osama bin Laden in 2002 discovered a massive tunnel complex connecting the natural Tora Bora cave formations in Afghanistan.
The tunnels in Gaza initially had some basic characteristics in common with other excavation sites in Israel and elsewhere in the world, such as burial caves, mines, and hiding systems. “But each tunnel system is different and uniquely related to the geological, geographic and geopolitical conditions in place,” he explained.
"What is interesting about Hamas is that the rate of growth of the tunnels, not only in size but also in purpose, complemented the development of the organization’s operational concept," Roskin said. "It began with the smuggling of goods, progressed to the smuggling of weapons, and later evolved into attack tunnels."
"At these stages, the organization’s perception was tactical. Later, they facilitated abductions like that of the 2006 kidnap of Private Gilad Shalit and transformed the underground into attack and hiding tunnels," he said.
"The next phase was the strategic offensive tunnels that were revealed during Operation Protective Edge nine years ago. These new tunnels corresponded to the growing operational appetite of Hamas, whose leaders saw that they were always successful – and that the Israel Defense Forces had only a meager response to this.”
Tunnels initially used for smuggling
THE FLEDGLING phase began in 1982 following the peace agreements with Egypt and Egyptian insistence that the border dissect the town of Rafah between Gaza and Egypt. Residents dug tunnels that were used to smuggle goods and mainly to reunite families that were split between the two sections of Rafah.
The tunnels at that time were not used for terrorism; they were dug mainly by local miners with experience in digging wells. In 1994, an upward trend began in the number of smuggling tunnels for goods and munitions between Rafah in Egypt and Rafah in Gaza, which came under the control of the Palestinian Authority as part of the Oslo Peace Accords.
In 2000, an intensification of the use of the underground began following the second Intifada (Palestinian uprising) and in view of the IDF’s preparations for an unfulfilled invasion of the Gaza Strip as part of Operation Defensive Shield. During this period, illegal arms smuggling and the mining of tunnels in Rafah increased.
Later, the realization that Israel had no effective response permeated Gaza, and Hamas and other players increased and developed underground activity, which included explosions under IDF positions through attack tunnels. After Israel’s full unilateral military and civilian withdrawal from the Gaza Strip in 2005 geared to allowing Gazans to independently build a new future, the investment in the IDF’s response to the tunnel challenge significantly decreased due to the erroneous Israeli assessment of an upcoming peaceful future for the people of Gaza, Roskin wrote.
“On the other hand, the smuggling tunnels between Egypt and Gaza expanded in quantity to hundreds, grew in size, length and quality – and larger spatial distribution [as well as] shafts for entry and exit were already established in designated and visible sheds, and legal and illegal goods freely passed through."
The Egyptians did not take measures to stop this profitable business and the arming of Gaza against Israel. Concrete supplied by Israel for construction was used to reinforce tunnel walls and not just wood planks as in the past. Thus, Gaza Palestinians and Hamas armed themselves and moved to independent manufacture of weapons from smuggled materials, and mining the offensive tunnels that were now directed towards Israel.
Takeover of the Gaza Strip
WITH THE violent Hamas takeover of the Gaza Strip in 2007 from the Palestinian Authority – and in the absence of significant interference from Israel or Egypt and following the successful abduction of Shalit – the field of underground warfare in Gaza expanded and developed into a holistic joint guerilla-terror warfare concept, the results of which we are now witnessing: access tunnels were dug to indirect ballistic rocket and mortar firing positions by 2007 and to smuggled goods, logistic centers and command and control headquarters.
From 2009, as part of its holistic approach, Hamas switched to strategic use of the underground and dug about 35 offensive tunnels under the 1949 armistice line (border) with Israel, some of which penetrate hundreds of meters into the Jewish state. These tunnels were no longer just long transit routes from point to point, but rather complex, multi-story underground caverns and tunnels with rooms, halls and warehouses. Many entrance shafts for the underground “city” – mainly in residential buildings – were horizontal, vertical or incline. In Gaza, a "tunnel culture" developed that included educational visits of pre- to high-school students, wedding photos and tours of the underground tunnel system.
It can be assumed that an extensive multi-story tunnel network of dozens and probably several hundreds of kilometers is spread under the Gaza Strip. Roskin noted that it’s difficult to map the tunnel network accurately from the surface or from space and that highly classified information is essential for 3D mapping and imagery visualization.
In fact, the expensive and sophisticated underground barrier erected by Israel on its side of the 1949 armistice line several years ago did significantly prevent Palestinian terrorists from infiltrating Israel through the underground – but it didn’t prevent the use and expansion of the tunnels in the Strip. So, on October 7, the barrier meant to keep Hamas terrorists out actually allowed them to reach the border zone via the underground tunnels without being revealed by IDF surveillance cameras.
Besides Israel's 2005 unilateral withdrawal from the Gaza Strip and its difficulty in locating the tunnels that enabled their development, Roskin points out Gaza’s geological features that facilitated mining. In the southern Gaza Strip there are sedimentological units, one to two meters thick of varying degrees of cohesion, formed from the accumulation of layers of dust and sand that harden and coalesce with time but do not turn into rock.
These units are relatively convenient for mining by hand, are stable enough and tend not to collapse. Until the 2000s, the tunnels were usually dug at a depth of four to 12 meters. Above a depth of four meters, they were not stable and there was usually no reason to invest and dig to depths of more than 12 to 15 meters. This was based on general observations and an incidental result of geophysical research in a simulated area, since the Israeli army never mapped or measured the tunnels in a professional and systemic manner.
BUT ROSKIN said that Hamas consistently learned and improved, and began digging deeper, bigger and longer specimens. At the same time, the means of support, communication and electricity and even human adaptation were close-to perfected.
“At first, it’s a psychologically and physiologically difficult place to be in. Beyond hiding the entrances and exits, the location of the tunnels in an urban area makes it easier for Hamas because the necessary infrastructure such as electricity, water and communications is nearby.," he said. "Even without an electricity network, air ventilation systems into the tunnels are possible with the help of underground generators."
Explaining the ease of mining together with the difficulty of detection, the geomorphologist noted that there are several technological detection methods, some of which are based on the transmission of a wave that may partially return according to the properties of the soil.
“But in this case, the search in a sense is for nothing, [since] a very small cross-sectional space of air compared to the subsoil medium, with a width and height of usually no more than one or two meters respectively [is] just enough to allow two-way movement in the underground, "Roskin said. "In addition, to activate detection, one has to be on ground above the tunnel or in the ground in the same place.”
Another approach to locating tunnels is identifying construction, maintenance and activity signs on the surface such as soil piles. “For this, you need high-resolution fusing of intelligence work looking at small changes in the terrain at short time intervals," he said. "In a built-up area this is very challenging. Within the city, these changes may be concealed within structures or swallowed up by intense daily reality/activity.”
It seems that until recently, popular perception of the Hamas tunnels was sometimes quite simplistic, Roskin said: they were treated as a passage for fighters, constituting a threatening infrastructure. But in recent years, Hamas integrated the underground system in many ways into its defensive and offensive system, built by cruelly combining military warfare, guerilla warfare and terrorism.
"This holistic guerilla-fare concept includes logistical, strategic and tactical tunnels alongside above-ground battle methods. The underground is integrated into all aspects of the battle, including gunfire, secretly concentrating forces and probably also for transporting prisoners and hostages and for holding them in secure medicinal conditions," he said, concluding that "These conditions are indeed a challenge for full offensive IDF treatment.