The Israeli military said the focus of its ground operations in Gaza is to destroy the labyrinth of tunnels from the strip into Israel that can be used for launching attacks. Israeli officials, who revealed that they had been planning for a year to destroy the tunnels, began their ground assault July 17, after 10 days of bombardment, when 13 Hamas gunmen emerged from one underground passage near a kibbutz in southern Israel.
Q: What is the strategic value of the tunnels?
A: In March, a former Hamas prime minister, Ismail Haniya, said in a speech before thousands of supporters in Gaza City that tunnels open "a new strategy in confronting the occupation and in the conflict with the enemy from underground and from above the ground." In June, five Palestinian militants were killed in an explosion in a tunnel in which they had been working. Hamas has long stored weapons underground.
Tunnels from Gaza to Israel have had a powerful hold on the Israeli psyche since 2006, when Hamas militants used one to capture an Israeli soldier, Gilad Shalit, who was held for five years before being released in a prisoner exchange.
Q: How many tunnels are there?
A: Since the incursion into Gaza, the Israeli military said, it has uncovered 23 tunnels with 66 access points, many of them in Shejaiya, a neighborhood of Gaza City close to the border with Israel. Lt. Col. Peter Lerner, a military spokesman, said the tunnels were near the periphery of Gaza, and that he believed there were "tens" more.
Q: What are the tunnels used for?
A: Some have been used by Palestinian militants to enter Israel, and there have been several deadly clashes between Israeli soldiers and militants emerging from tunnels on the Israeli side of the border. On Saturday July 19, two Israeli soldiers and one Hamas militant were killed when Palestinian fighters slipped into Israel through a tunnel and attacked a border patrol before the militants retreated underground, back into Gaza.
Several other "offensive tunnels," as the military calls them, have been discovered in the past few years, some of them packed with explosives. In 2012, an explosion in one tunnel wounded a soldier and destroyed an army jeep. In 2013, the army discovered a mile-long tunnel leading from a house in Gaza to Kibbutz Ein Hashlosha. It had electricity and a telephone line. In March, the army found another tunnel that it said looked like a subway passage. "Hamas has vast experience of utilizing these types of things," Col. Lerner said at the time, "whether it's for infiltration, detonation or abduction."
Q: How are they constructed?
A: The Israeli military has described tunnels from Gaza to Israel as "complex and advanced," with many offshoots in different directions. Destroying them, the military said, is a technological and operational challenge. The tunnels can be as much as 90 feet underground and reinforced with concrete, a scarce commodity in Gaza, where most imports of construction material are banned by Israel, except for internationally supervised projects. The material -- the military estimates 600,000 tons -- may have come through different smuggling tunnels from Egypt or have been diverted from its intended purpose. The lack of concrete for building has left many Gazans unable to rebuild their homes and hampered construction projects that provide Gazans with jobs.
In March, the Israeli military uncovered what it called "the most advanced tunnel," which stretched hundreds of yards into its territory from the Gaza Strip and could have been used to attack or capture Israelis. Though the tunnel did not reach an Israeli town or village, Col. Lerner said, "it wasn't that far -- a quick sprint, and you could attack a community."
But a spokesman for Hamas, the militant Palestinian faction that controls the Gaza Strip, said the tunnel was "unsuitable for use."