In early 2018, after four years of increasingly frantic effort, Israel announced that it had perfected what some generals were calling the “Steel Dome” system to reliably detect when terrorists, or anyone, was building tunnels into Israel. “Steel Dome” is a play on the name of the Iron Dome anti-rocket system. The anti-tunnel system proved more difficult to develop because it involved detecting tunnel construction by Palestinian groups that have been doing it for over a decade and have developed a certain expertise and resourcefulness in adapting to countermeasures. The Gaza tunnel builders were the most skilled and they were exporting their expertise to tunnel builders in Lebanon, Syria and the West Bank. So there was a sense of urgency in getting Steel Dome to work.
Technical details on Steel Dome are scarce but it apparently uses improved underground sensors (both permanent and portable) plus airborne sensors as well. The Israelis apparently drew upon the enormous amount of work done on detecting oil and gas deposits. This field gets enormous attention, and funding, because finding oil and gas is a really big business. This industry has benefitted greatly from increased (and inexpensive) computer capabilities and much improved statistical and analytical software to make something of huge quantities of data. Israeli firms have been leaders in both hardware and software and that give Israelis the opportunity to apply much of that seismological research to the detection of clandestine tunnel building. Apparently the Israelis had a breakthrough because they found, and destroyed three well-hidden Hamas tunnels in two months. The third tunnel was destroyed on January 14th and this one tried to hide itself by passing under an Egyptian natural gas pipeline that crossed the Israeli border where the borders of Gaza, Israel and Egypt meet. This tunnel was detected using the portable and airborne sensors. The partially underground Gaza border fence will be completed by 2019.
In 2016, faced with all this despite increased Israeli efforts to prevent successful tunnel building the Israeli government accelerated the long planned but constantly delayed project to build a high tech detection and barrier system to prevent Hamas from building tunnels into Israel. Since 2015 this system, called “Obstacle”, had been in the works. But actual construction was repeatedly delayed after it was discovered that Obstacle would cost over $10 million per kilometer and this underground barrier had to cover 65 kilometers of Gaza border.
The Defense Ministry kept telling those living or working near the Gaza border that the project was delayed because of more urgent defense needs. OK, that has been a common problem throughout Israeli history. Then in early 2016 local civilians began reporting (and recording) the sound of tunneling under building near the Gaza border and demanded action. This tunneling activity was confirmed by Israeli intelligence, which used an informant network in Gaza to confirm the increased tunneling activity. Israeli intel took advantage of that fact that a growing number of Palestinians were getting out of Gaza (where the economy had collapsed partly to support the tunnel building). Some of these recent Gaza residents had worked on the tunnels and were able to confirm the source of the border noise. Some of the Gaza refugees were willing to provide detailed information on how Hamas was going about it. Israel confirmed enough of this new information and realized that the only workable defense against these tunnels into Israel (for kidnapping Israelis and carrying out terror attacks) was to scrounge up the cash and proceed with Obstacle. This includes an upgraded security fence along the Gaza border that would employ new sensors and a computer network that would not only assemble sensor data but also rapidly indicate where more scrutiny, or counter-tunnel efforts were required.
All this tunnel anxiety began in 2014 as an after-effect of the mid-year “50-Day War” between Hamas and Israel. The discovery of how much Israel had underestimated the Hamas tunnel system led the Israeli government to promise something that eventually evolved into Obstacle. This was mainly to detect new cross border tunnels Hamas was certain to build after war. Israel had known of Hamas use of tunnels since 2004. Until 2009 most of the tunnels were for smuggling people and goods from Egypt to Gaza. But in 2014 Israel became aware that Hamas was building many more tunnels into Israel as part of a major terror and kidnapping operation. During the 50 Day War Israel found and destroyed dozens of tunnels before leaving Gaza. In order to calm down the thousands of Israelis living near the Gaza border Israel promised to make additions to the Gaza security fence to prevent (or greatly reduce the possibility of) any future Hamas tunnels into Israel.
Another response to tunnel anxiety is the new “tunnel warfare” course the army is giving to troops. This is justified by the extent to which anti-Israel Islamic terror groups have adopted the use of tunnels to get into Israel and shelter their forces when attacked by Israel. Thus the Israeli Army is now giving all their combat troops training in detecting, destroying and fighting in tunnels. To facilitate the training of over 100,000 active duty and reserve troops the army is spending several million dollars to build ten tunnel training facilities. In addition to realistic sections of tunnel, where troops can also use their weapons, there is also a highly detailed computer simulator for planning and carrying out a combat operation against an enemy tunnel.
The main problem Obstacle has to deal with is that over the years Hamas has learned how to dig tunnels that were virtually undetectable. This meant going deep enough to avoid detection by ground penetrating radar or acoustic sensors. This makes it more expensive and time consuming to build tunnels but Hamas diverted much foreign aid (cash and building materials) to the tunnel effort and continues to do so. These detection problems were largely solved with better software to make the most out of the deeper sensors the Steel Dome fence used.
Before the ground invasion in 2014 Israel had been searching for the Hamas tunnels but had only found four of them after two years of effort. In early 2014 Israeli troops found one that was 1,800 meters long and extended 300 meters into Israel. Hamas dismissed this find as a tunnel that had been abandoned because of a partial collapse. But the Israelis said the tunnel had been worked on recently and equipment, like generators, was found in it. The tunnel was lined with reinforcing concrete and was 9-20 meters (30-63 feet) underground. Three of these tunnels were near the town of Khan Younis and apparently part of a plan to kidnap Israelis for use in trades (for prisoner or whatever) with Israel. Israeli intelligence knew Hamas leaders were discussing a much larger tunnel program, involving dozens of tunnels. Most tunnels had no exits in Israel and those were created just before the terrorists were to use them for a nighttime raid into Israel to kill and kidnap. Available tunnel monitoring equipment was slow and often ineffective if there was no one actively working on the tunnel below or if there was no exit (yet) on the Israeli side. That meant Hamas had been building and “stockpiling” these tunnels for at least two years and most of the completed ones could only be detected inside Gaza, where their entrances were. These were also hidden, at least from aerial observation. Israeli intelligence had discovered some of these entrances by detecting the Hamas activity around the entrances (entering and leaving, removing dirt). Hamas tried to hide this activity and Israel knew this meant they probably succeeded in some cases. Thus before the Israeli troops went into Gaza in 2014 commanders had lots of information of where to look. Israeli combat engineers had been trained to destroy the tunnels, which was not easy because Hamas had booby-trapped some of them.
Since the war ended in August 2014 Hamas has gone back to building more tunnels and inspiring other Islamic terror groups to do the same. Hezbollah in Lebanon took the hint is now digging them under the Lebanese border into Israel. So Israel is taking the threat seriously and training most combat troops to deal with it is part of the response while furiously working towards perfecting the software that would make Steel Dome consistently accurate and reliable. .
The turning point came on January 14th when Israel destroyed another Hamas “attack tunnel” that had gone under the border into Israel near the Kerem Shalom border crossing, close to the Egyptian border and is the main crossing for all foreign aid. An airstrike was used to collapse the tunnel and an Israeli general later revealed that Israel was capable of detecting any tunneling efforts and that all such existing tunnels would be found and destroyed by the end of the year. The Israelis believe Hamas will now switch to more rockets, suicide bombers and efforts to operate from the sea.