Tunnel beneath the Egyptian-Gaza border
Tunnel beneath the Egyptian-Gaza borderAbed Rahim Khatib/Flash90

Background:

The invasion and massacre on Israel on October 7 brutally demonstrated how Hamas has significantly tactically and strategically improved and strengthened its terror capabilities since it began to root itself in the Gaza Strip in the 2000s. The well-known "Hamas tunnels" played a central role in this development.

Prof. Joel Roskin, of Bar-Ilan University in Israel, has followed the "evolution" of the Gaza tunnels for years and analyzed the conditions that allowed their formation and expansion. Prof. Roskin specializes in sand and dune geomorphology; military geosciences, geoarchaeology, portable OSL. He can be contacted at [email protected]

In 2020 Roskin, a geomorphologist and geologist from the Department of Geography and Environment at Bar-Ilan University, published a book chapter based on his study "Underground Warfare in the Gaza Strip and the Military Complexity of Combating It". An article on the same topic is currently in the final stages of acceptance by the academic journal Studies in Conflict and Terrorism. The article describes the field data and the geopolitical conditions that literally provided the fertile ground for the development of the tunnels. It is based on Prof. Roskin's experience as head of the terrain research department at the Southern Command in the 2000s, and on information publicized in the media.

Report:

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. "However," says Prof. Roskin, "each tunnel system is different and uniquely related to the geological, geographic and geopolitical conditions in place. 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. 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. The next phase was the strategic offensive tunnels that were revealed during Operation Protective Edge in 2014. 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 (IDF) had only a meager response to this.

As mentioned, the tunnels in Gaza developed in several stages, each of which is described as related to geopolitical development in the region. 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 were not then used for terrorism and 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 Palestinian Arab uprising (Intifada) 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 allow 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.

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, 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 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 Palestinian Arabs 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.

With the violent Hamas takeover of the Gaza Strip in 2007 from the Palestinian Authority (The War of Gaza), in the absence of significant interference from Israel or Egypt, and following the successful abduction of Gilad 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 currently witnessing: access tunnels to indirect ballistic rocket and mortar firing positions by 2007 and to smuggled goods, logistic centers and command and control headquarters were dug.

From 2009, as part of its holistic approach, Hamas switched to strategic use of the underground and dug under the 1949 armistice line (border) with Israel about 35 offensive tunnels, some of which penetrate hundreds of meters into Israel. 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.

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It can be assumed that an extensive multi-story tunnel network of tens and probably several hundreds of kilometers is spread under the Gaza Strip. It is difficult to map the tunnel network accurately from the surface or space and that highly classified information is essential for 3D mapping and imagery visualization. Indeed, the expensive and sophisticated underground barrier erected by Israel on its side of the 1949 armistice line, several years ago, did significantly prevent Palestinian Arab terrorists from infiltrating Israel through the underground. However, it did not prevent the use and expansion of the tunnels in the Strip and on October 7th it allowed Hamas terrorists to reach the border zone by underground, without being revealed by IDF surveillance cameras.

Not only did Israel's 2005 unilateral withdrawal from the Gaza Strip and its subsequent difficulty in locating the tunnels enable their development. the geological features of Gaza facilitated mining. In the southern Gaza Strip there are sedimentological units, 1-2 m thick of varying degrees of cohesion, which are formed from the accumulation of layers of dust and sand that harden and coalesce with time but do not turn into rock. They are relatively convenient for manual mining on the one hand, and stable enough and tend not to collapse on the other hand.

Until the 2000s, the tunnels were usually dug at a depth of 4-12 meters. Above a depth of 4 m they were not stable and there was usually no reason to invest and dig to depths of more than 12-15 m (this is a determination 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 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.

Tunnel cross-section sketch
Tunnel cross-section sketchProf. Roskin

At first, it's a psychologically and physiologically difficult place to be in. But, 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. Even if there is no electricity network, air ventilation systems into the tunnels are possible with the help of generators, positioned underground.

How does the ease of mining reconcile with the difficulty of detection? 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, 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 – just enough to allow two-way movement in the underground. 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. Here you need high-resolution fusing of intelligence work looking at small changes in the terrain at short time intervals: 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: they were treated as a passage for fighters, constituting a threatening infrastructure. In recent years, Hamas integrated the underground system in many ways into its defensive and offensive system, which is 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. These conditions are indeed a challenge for full offensive IDF treatment.