One after-effect of the 2014 “50-Day War” between Hamas and Israel was an Israeli government promise to develop and add additional detection capabilities to the existing security fence around Gaza. This was mainly to detect new cross border tunnels Hamas was certain to build after war. Israel has 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. 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. Work has not yet begun on the anti-tunnel features, in part because it was soon discovered that this effort would cost about $700 million. The Defense Ministry kept telling those living or working near the Gaza border that the project was delayed because of more urgent defense needs. But recently local civilians reported (and recorded) the sound of tunneling under building near the Gaza border and demanded action. The media jumped all over this but so far the military says it has investigated each report and so far has found no tunnels. So far this year Hamas has admitted losing at least nine of its men in tunnel construction accidents.
To further increase anxiety along the Gaza border there is a 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.
All this tunnel anxiety began in 2014 when Israel made it clear that one of the primary objectives of the 50 Day War with Hamas was to find and destroy all the tunnels Hamas had dug into Israel over the previous few years. This could only be accomplished if Israeli troops were inside Gaza and able to search for the places where the tunnels start. Over the years Hamas has learned how to dig tunnels that were virtually undetectable on the Israeli side. 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.
Before the ground invasion Israel had been searching for the Hamas tunnels but had only found four of them after two years of searching. 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. 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 recently, 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. Israel suspected there were over fifty of these tunnels and troops remained inside Gaza during August 2014 until all of the tunnels into Israel were found. This effort also included collecting information on how they are built and how they could be detected from the ground or air. If Israel knows where a tunnel is, before they destroy it they can run some tests with their sensors and that knowledge will make it more difficult for Hamas to build new tunnels. Israel eventually found 31 tunnels from Gaza to Israel and improved their detection capabilities.
Since the war ended in August 2014 Hamas has gone back to building more tunnels. Hezbollah in Lebanon was inspired by the Hamas use of tunnels and 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.