WASHINGTON – Israel was aware that Hamas militants were creating a network of tunnels underneath Gaza in recent years but the extent and sophistication of the network and its potential threat has taken the Israeli military by surprise, Israeli military experts say.
Before the announcement of a 72-hour cease-fire between Israel and Hamas, Israeli Prime Minister Benjamin Netanyahu had vowed Thursday to complete the destruction of the tunnel network. Israel said it has identified about 32 tunnels and destroyed more than half since it launched a ground offensive to dismantle them on July 17.
The Israel Defense Forces (IDF) said it would take several more days to complete the destruction of all known tunnels.
Israel began its military strikes on July 8 in response to rocket fire from Gaza, but the IDF said the primary mission of the fight had shifted to demolishing Hamas' tunnels, which pose a greater threat to Israel because the U.S.-designated terrorist group uses them to sneak militants into Israel and attack troops or civilians.
"This is a strategic threat," said Yossi Alpher, a military analyst and former Israeli intelligence official. He said Israel's intelligence services knew of the tunnels but didn't recognize the potential threat they posed until the current conflict started.
"In intelligence, there is known facts and then interpreting their strategic impact," he said.
Most of the incoming rockets have been intercepted by the Iron Dome defense system, but the threat from militants sneaking into Israel is harder to detect. Earlier this week, five Israeli soldier were killed on the Gaza border by militants who emerged from a tunnel.
Last week, the IDF said it killed 10 militants who emerged from a tunnel and attempted to infiltrate a kibbutz.
In addition to infiltrating Israel, the tunnels are used by Hamas to hide weapons, move militants and communicate. Most tunnels are reinforced by concrete, and some have rails for moving supplies. Dozens of small access points have been discovered, including at least one inside a mosque, according to the IDF.
Hamas had used tunnels before, but primarily for smuggling supplies from Sinai into Gaza. Still, there were signs as far back as 2006 that Hamas saw other uses for tunnels. At the time, militants used a tunnel to launch a cross-border raid that led to the capture of an Israeli soldier, Gilad Shalit. He was held for five years until he was exchanged for more than 1,000 Hamas prisoners.
Recently, Hamas has embarked on a major effort to build tunnels. The construction of the tunnels has "become a major industry in Gaza," said Jeff White, a former Defense Intelligence Agency official and a defense analyst at the Washington Institute for Near East Policy.
There is a long history of tunnels being used by guerrilla and other irregular forces. U.S. soldiers encountered an elaborate network of tunnels built by the Viet Cong in the Cu Chi district of Saigon, now Ho Chi Minh City.
To clear the Viet Cong tunnels, U.S. soldiers, called tunnel rats, had to climb into them armed with little more than a pistol and a flashlight.
Today, destroying tunnels remains labor intensive and dangerous work, though techniques and technology have improved.
Tunnels cannot be easily identified by air and cannot be fully destroyed by bombing. If the entire tunnel is not collapsed, it can be quickly put back into service.
"It's a pretty serious process," said Capt. Eytan Buchman, an IDF spokesman. "It's not just a dropping a bomb from an aircraft."
Destroying the tunnels typically requires specially trained combat engineers who are aided by robots and trained dogs to explore the tunnels. Earth-moving equipment and explosives are used to collapse them.
"It is important to remember that this is a significant operational and engineering challenge," Israeli Maj. Gen. Sami Turgeman said, according to Ynet, an Israeli news website.