Shortly before the truce came into force last week, two Hamas operatives emerged from an “attack tunnel” in the Beit Hanoun area of northern Gaza to engage IDF troops after surviving more than a month underground.
Both were killed and the tunnel destroyed before they could inflict serious damage, according to a well-placed IDF official.
“Last week we got some fire around us while looking into a tunnel,” said the official. “It’s really hard to believe; they probably live off of dates and water and they haven’t seen the light for almost two months now.”
Combat engineers from the IDF’s 252 and 551 divisions have been intensively searching the northern part of the Gaza Strip for tunnels and booby traps since the land incursion started in late October.
The area is heavily fortified with improvised explosive devices and attack tunnels as Hamas had always anticipated the IDF rolling into the area after the Oct 7 attack.
It is still unknown exactly how many tunnels there are in Gaza but in the north, said the IDF official, “there are almost as many tunnels as there are roads”.
“It’s hard to say what’s connected to what. We only see the entrances to the tunnels and we research as far as our technology allows us into the tunnel. It gives us enough of a picture to know that there are at least dozens of tunnels in our area.”
There are three main types of tunnel dug into the soft sand and clay soil of Gaza, according to the IDF: defensive; offensive; and tunnels that go under the fence to Israel and Egypt.
All the major cross-border tunnels are now believed to have been blocked or destroyed.
The deeper and more elaborate defensive tunnels, like the one recently revealed under the Al-Shifa hospital with its bunkers and store rooms, are thought to be dug within the most populated parts of the Gaza Strip.
This allows Hamas to utilise the protection offered by civilians and civilian infrastructure to the maximum.
In contrast, in the northern area of the strip, most of the tunnels that have so far been uncovered are designed for attack, said the IDF official.
Typically they will be relatively short but large enough to allow several fighters to hide for a lengthy period before springing up and catching IDF troops by surprise.
Although they are not as intricate as the defensive tunnels uncovered further into Gaza, they are sophisticated pieces of engineering and often have explosive booby traps dug into their structure by design.
“We encounter a lot of booby traps, in buildings, as well as in and around tunnels,” said the IDF official. “Some of them are improvised but a lot of them are built into the structure, meaning we found explosive devices that aren’t improvised cemented into walls”.
While some of these devices are inside the tunnels themselves, others are “above ground in bottlenecks, meaning places you have to go through to reach the tunnel or facing a tunnel entrance”.
The devices are operated by “pull strings”, as well as other more sophisticated triggers, such as infrared lights, according to the IDF.
One such device, which it is thought incorporated a camera to allow for its remote operation, killed five IDF soldiers in the Beit Hanoun area of Gaza in mid-November.
The blast came from a large device hidden by a tunnel entrance adjacent to a mosque and was detonated as the soldiers moved towards it.
“One of the things we try to do is avoid the bombing of mosques and schools, and other sensitive buildings but that leaves these devices intact,” said the IDF source.
Once tunnels are located and de-mined, they are destroyed by IDF combat engineers.
Officials are unable to talk in detail about the technologies being used but it has been reported that an “explosive gel” has been poured into several tunnel entrances and allowed to spread throughout the network before being detonated.
This is said to ensure that the entire tunnel system is destroyed rather than just a part of it.
In terms of completely destroying tunnels as some of the video images emerging from northern Gaza have suggested, the IDF official said: “We have a lot of different technologies. Some of them are experimental, some of them are tried and true from the last war in 2014. But what I can say is that they work. The answer is 100 per cent, yes.”