Sept. 24, 2008: A Palestinian smuggler holds a light inside a tunnel beneath the Egyptian-Gaza border.
2: Aug. 1, 2007: A Palestinian tunnel digger, wearing a mask to conceal his identity, removes sand in a bucket from a tunnel underground in Rafah, in the southern Gaza Strip.
Oct. 21, 2008: A Palestinian smuggler holds a torch inside a tunnel beneath the Egyptian-Gaza border.
Nov. 17, 2008: A Palestinian smuggler prepares to smuggle fuel into Gaza through a tunnel beneath the Egyptian-Gaza border.
A massive tunnel system running from Gaza to the Egyptian border has long served Palestinians as a supply line for everything from livestock and construction materials to stocks of medicine and smuggled electronics equipment. But now, as war rages in the area, the tunnels have become the main route for providing the Hamas terror group with the weapons it needs to fight against Israel.
Dismantling the tunnels in Gaza is a key to winning the war for Israel, which has sworn to eradicate them. But military experts and historians say destroying them will be virtually impossible.
The tunnel system is strikingly similar to the Viet Cong's infamous Cu Chi tunnels during the Vietnam War. The Viet Cong moved weapons and supplies through their tunnels, and, like Hamas, they hid their top leaders in them as well.
The Viet Cong — a technological underdog to the United States — was able to bridge the firepower gap against a world superpower through sheer cunning and ingenuity. The Cu Chi tunnels were a vast network of underground sleeping quarters, weapon storage facilities, war rooms and fighting positions. Guerrillas dug out makeshift medical facilities beneath the earth, and doctors tended to wounded soldiers in them, often using electricity generated by a bicycle.
The Viet Cong planned and executed attacks from beneath the surface, and the U.S. military launched two tunnel-specific offensives to eradicate them. But both Operation Crimp and Operation Cedar Falls met with mixed results, and the goal of sealing off the tunnels proved elusive at best.
Australians and Americans used gas, water and explosives to exterminate the threat from below, but even aerial carpet-bombing proved ineffective for underground paths that ran as deep as 60 feet. Like the boots on the ground necessary to physically root out an opposing force, the tunnels required painstaking personal attention.
The Australians used infantrymen they named "tunnel rats" to descend into the mazes and engage the enemy. They performed admirably, despite exploding booby-trapped hatches and steep drops where soiled and sharpened bamboo sticks could skewer a soldier. But the clandestine subterranean insurgency persisted.
Now, nearly 40 years later, Israeli forces face a similar threat, with obstacles that have not changed.
"Hamas' tunnels systems as a tactic within the urban guerrilla-style warfare, were known to the [Israeli forces] for more than two years in which the appropriate operational tactics were developed and adopted," said retired Col. Yoni Fighel, a senior researcher at the International Policy Institute for Counter-Terrorism, at the Interdisciplinary Center in Herzliya, Israel.
Fighel refused to comment on specifics, but he said in an e-mail that Israeli "urban combat tactics were adapted, special technologies developed."
He also warned not to "confuse the 'smuggling' tunnels from Egypt and the 'combat' tunnels," insisting that one system has a tactical use, while the other is of mixed commercial use.
But Nir T. Boms from the Center for Freedom in the Middle East — a Washington think tank formed by Americans of Middle East descent — found it difficult to separate commercial smuggling from Hamas' covert activities. "It depends on the who owns the tunnels and for what purpose," he said.
A major distinction between the tunnels under Gaza and the Viet Cong underground network is that some of the Gaza tunnels conduct commercial activity between Gaza and Egypt. "There is an economy of the tunnels, with each tunnel having a type of owner charging a 'toll' for passage," Boms told FOXNews.com in a phone interview.
"The cost of digging a tunnel is roughly $3,000," said Boms.
There's no consensus on precisely how many tunnels and underground caches exist. Some experts say there are approximately 800 clandestine passages; others say there are well over 1,000.
Gazans call the tunnels a lifeline to the outside world, as they facilitate the commercial traffic of a variety of products. The growing network has been described as an underground bazaar, with everything from iPods to Viagra traveling into Gaza at substantially marked-up prices. But Israeli intelligence says rockets and arm shipments also make it through the tunnels.
"They build bunkers and weapons storage space under their homes," said Boms.
Finding and destroying the Hamas network of tunnels will be difficult, and Israelis know this better than most. In the 7th century B.C., the Bible recounts how the Hebrew King Hezekiah, in anticipation of a siege of Jerusalem by the Assyrians, constructed an underground passage to preserve access to a crucial supply of water for the city. In present day Israel, that ancient man-made tunnel, much like the Cu Chi tunnels in Vietnam, still exits. To this day, the winners of both those conflicts allow tourists to view and explore the marvels of the underground defenses that helped to defeat the enemy.
Israel nonetheless has set a goal of eradicating the underground tunnels as a means of crippling Hamas.
"We must reach, at the end of the war, a situation in which this arms smuggling is stopped," Yossi Peled, a general in the Israeli reserves and former head of the Israel Defense Forces' northern command, said recently on Israeli radio. "If we do not achieve this, then one might very well ask why it was that we embarked on this war to begin with."