Some battlefields are measured in miles of front line, and some are measured in feet of concrete, earth and darkness. In the latest episode of the Israel Defense Forces series IDF: Mission Brief, a company commander identified only as Captain B. describes the second kind of battlefield. He serves in the IDF’s Special Operations Engineering Unit, the formation better known by its Hebrew name, Yahalom. Its soldiers are the troops sent forward when the fighting goes underground, into tunnels built to hide fighters, weapons and hostages.
The interview is short, but the job it describes is one of the defining military problems of Israel’s recent wars. Hamas in Gaza and Hezbollah in Lebanon both spent years digging networks beneath homes, farms and border villages. Those tunnels changed what ground forces had to do before they could move, fight or search a building. Yahalom exists because ordinary infantry and ordinary engineers were never designed to solve that problem alone.
An Engineering Unit Built for the Underground
Yahalom is the special unit of the IDF’s Combat Engineering Corps, trained for missions that combine demolitions, robotics, bomb disposal and underground warfare. Its name is Hebrew for diamond, and its work is deliberately narrow and technical. Within the unit, a sub-unit known as Samur, the Hebrew word for weasel, has specialised in entering, clearing and destroying tunnels since 2004. That specialisation began long before tunnels became the headline problem they are today.
The skills involved go well beyond blowing an entrance closed. Tunnel soldiers must map a passage they cannot see from the surface, often working from intelligence fragments, drilling, sensors and cautious exploration. They must assume that shafts are booby-trapped and that side passages hide fighters or explosives. They work in heat, dust and darkness, in spaces too tight for normal equipment and tactics. It is slow, claustrophobic work performed under the constant possibility of collapse or ambush.
Recruitment reflects those demands. Reporting on the tunnel teams has described soldiers selected for patience, technical aptitude and an ability to stay calm in confined spaces. The work rewards methodical personalities rather than aggression, because a rushed decision underground can kill the team making it. Every metre gained has to be checked, marked and understood before the next metre is attempted. In that sense the unit fights more like investigators than assault troops, even when the mission ends in combat.
Gaza: A City Beneath a City
Gaza presented the underground problem at its largest scale. Israeli officials and independent analysts have estimated the Hamas tunnel network at somewhere between roughly 250 and 500 kilometres in total length, although no outside observer can verify a precise figure. In 2021 the IDF said it had destroyed more than 100 kilometres of tunnels, while Gaza’s Hamas leader at the time claimed the network ran to 500 kilometres and had been only slightly damaged. The competing numbers themselves show how difficult the system was to measure. Much of it ran beneath densely populated civilian areas, which complicated every decision about how to find and destroy it.
Captain B. describes operating in Gaza across that kind of terrain, where a tunnel entrance might sit inside a home, a school compound or a patch of farmland. Engineering teams had to distinguish smuggling passages, command rooms, weapons stores and living quarters built for long stays underground. Some routes discovered during the war contained workshops, supplies and multiple branches leading in different directions. Destroying one shaft rarely ended the problem, because a well-built network was designed with alternate exits. The unit’s task was therefore to understand a system, not just to demolish a hole.
The most sensitive Gaza missions involved hostages. Yahalom teams took part in operations to locate and recover Israelis seized on October 7, including searches of concealed passages hidden behind false walls and reinforced doors. In one widely reported 2024 operation, combat engineers helped reach a hidden passage where the bodies of six hostages were recovered from a tunnel about ten metres below the surface. Operations like that explain why the unit trains for rescue and recovery as well as destruction. Underground, the difference between a weapons cache and a place where a hostage was held can be a single sealed door.
Lebanon: A Second Underground Front
The same skills were demanded in southern Lebanon, where Hezbollah built its own underground infrastructure near Israel’s northern border. Captain B. speaks about dismantling parts of that network, which Israeli forces say included staging routes, storage sites and positions prepared for attacks on northern communities. In operations reported in October 2026, Yahalom fighters worked alongside Brigade 7 troops to locate and demolish underground routes stretching hundreds of metres. Searches of those routes turned up living quarters, rifles, machine guns, launch positions and anti-tank missiles. Each discovery reinforced the IDF’s argument that the tunnels were military infrastructure, not simple hiding places.
Fighting tunnels on two fronts stretched the logic that produced the unit in the first place. Gaza’s network grew under a blockaded coastal strip, while Hezbollah’s grew across a land border with support from Iran. The engineering problems, however, rhyme: hidden entrances, booby traps, branching routes and infrastructure placed near civilians. A unit that learned its trade in one theatre could transfer hard lessons to the other. That transfer of experience is part of why such a small formation carries an outsized role.
Why This Small Unit Matters So Much
Yahalom’s importance is a measure of how warfare in the region has changed. Missiles and drones dominate headlines, but tunnels decide whether ground forces can move safely and whether an armed group can survive bombardment. A tunnel network lets fighters reposition, store weapons and emerge where defenders do not expect them. It also forces an attacker to slow down, expose engineers and spend enormous effort on ground that produces no dramatic images. For Israel, neutralising that system became a condition for almost every other objective in Gaza and along the northern border.
There is also a human reality that Captain B.’s account brings forward. Underground operations are carried out by young soldiers led by officers who know that mistakes are measured in funerals, including the funerals of the hostages they hope to find alive. The work is technical, but it is not sterile, and it takes place in the most dangerous spaces either side has created. Mission Brief is an IDF production, so it presents the unit’s own view of its mission, and claims about operations should be read in that light. Even with that caution, the episode is a useful window into a form of warfare that is usually discussed only in statistics about kilometres of tunnel destroyed.
As long as armed groups in the region invest in going underground, Israel will keep investing in the soldiers trained to follow them there. Yahalom began as a niche engineering formation and has become central to how the IDF plans ground operations. Its story is really the story of a battlefield moving downward, out of sight, where patience and engineering matter as much as firepower. Captain B. and his soldiers work on that battlefield every day, beyond the surface and largely beyond public view.
Source: Israel Defense Forces
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