Long, but well worth the read.
Israel launched its bloody offensive in Gaza to stop Hamas from lobbing missiles at major cities like Tel Aviv. The biggest challenge to the vaunted Israeli army, though, is coming from the ground, not the air: a sophisticated network of Hamas tunnels that have surprised Israeli security officials, caused a huge number of military fatalities, and struck fear into the hearts of many ordinary Israelis.
Israeli military, intelligence, and political officials have known for years that Hamas fighters were burrowing into their country from Gaza through underground tunnels. An Israeli army spokesman said this month that the military had discovered four tunnels just in the past 18 months, well before Israel's current ground offensive began. But in interviews, current and former Israeli officials said the military and intelligence services didn't realize the extent of Hamas's subterranean operations, nor did political leaders act to counter a threat that has become the central focus of Israel's Gaza campaign and stands as potentially the biggest Israeli intelligence failure in years.
A senior Israeli official, speaking on condition of anonymity, said the military has so far discovered far more tunnels -- 40 and counting -- than Israel had previously thought existed. The number came as a surprise, as did the sophistication of the tunnel network. Current and former officials said that Israeli intelligence and political leaders knew that the tunnels were fortified with concrete and had space to store weapons and food. But Israeli intelligence analysts and political leaders didn't comprehend that the tunnels were wide enough to move several Hamas fighters into the country at a time, and they didn't realize how many of the tunnels ended up in Israel, particularly near civilians. (A Hamas video that shows fighters emerging from a tunnel and attacking an Israeli military installation provides a vivid example of why Israelis have so come to fear the clandestine attacks.)
Read more: http://thecable.foreignpolicy.com/posts/2014/07/31/extensive_hamas_tunnel_network_points_to_israeli_intelligence_failure_harris