Peering Into Darkness Beneath the Israel

Through a watermelon field, about a mile from Kibbutz Nir Am in Israel, and less than half a mile from the Gaza border, there is a hole in the ground that plunges more than 40 feet into a tunnel that an Israeli officer described as 'big enough for a man in full body armor to go through standing up.'

This underground passage, discovered by the Israel Defense Forces two months ago, is similar to the 30 tunnels with more than 100 access points used by Palestinian militants to infiltrate Israel that have been discovered or destroyed since the military began its ground invasion of the Gaza Strip last week.

'We prevented a major terror attack by finding this tunnel,' said Max, 35, a lieutenant colonel in the I.D.F.'s chief engineer's office who, under military protocol, did not provide his last name. 'Hamas could have put through dozens, even hundreds of terrorists through this tunnel out on the Israeli side before we could have discovered it,' he added, according to a pool report.

Israel has said that the focus of its offensive is to destroy the labyrinth of tunnels from the strip into Israel that can be used for storing weapons or launching attacks. On Friday, the I.D.F. took reporters into a 6-foot-by-2-foot tunnel that runs almost two miles under the border to a greenhouse in Khan Younis to show the threat that the tunnels pose, and the difficulty that Israel has in ferreting them out and destroying them.

Hamas, the Islamic militant group that controls Gaza, has used its intricate system of tunnels to store weapons and preserve the element of surprise against the better-equipped, technologically superior Israeli military. Ismail Haniya, a former Hamas prime minister, said in a speech in March in Gaza City that the tunnels open ' a new strategy in confronting the occupation and in the conflict with the enemy from underground and from above the ground.'

Some tunnels 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.

It was an attack by 13 Hamas gunmen who emerged from one underground passage near a kibbutz in southern Israel on July 17 that prompted Israel to begin its ground assault after 10 days of aerial bombardment. Though that effort was thwarted, another surprise attack two days later killed two Israeli soldiers and one militant when Palestinian fighters slipped into Israel through another tunnel and attacked a border patrol before militants retreated underground into Gaza.

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.

The tunnels can be quite elaborate. The tunnel toured by journalists on Friday was reinforced with concrete and had a rack on the wall for electrical wiring. It also featured a metal track along the floor, used by carts that removed dirt during the tunnel's construction, that could be used to ferry equipment and weapons, the Israeli military said.

Israeli officials acknowledge that it is a difficult technological and operational challenge to destroy all of the subterranean passageways and neutralize the threat they pose. The tunnels are well hidden, said the officer who conducted the tour on Friday, and some tunnels are booby-trapped.

'We are confident we can destroy all or most of the tunnels,' the officer said, 'at least the ones we know about.'