DEEP beneath the ground Hamas terrorists lurk in a mysterious 311-mile maze of tunnels riddled with deadly traps.
The complex network has sprawled since the terror group clawed control of the Gaza Strip in 2007 and is feared to be being used to hide terrified hostages.
After unleashing carnage in Israel, thousands of cowardly Hamas militants retreated to the vast underground labyrinth and are thought to have taken with them dozens of abducted captives, including children snatched from their murdered parents.
Israel's military retaliated with a barrage of airstrikes - but need to unleash an all-out ground assault to reach terrorists hidden in the network.
Jonathan Conricus, an Israel Defence Forces (IDF) spokesman, said: "Think of the Gaza Strip as one layer for civilians and then another layer for Hamas.
"We are trying to get to that second layer that Hamas has built.
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"These aren't bunkers for Gazan civilians. It's only for Hamas and other terrorists so that they can continue to fire rockets at Israel, to plan operations, to launch terrorists into Israel."
The terror group began building its defensive tunnels - dubbed "Gaza Metro" - almost two decades ago in a bid to dodge Israeli rocket attacks.
Hidden up to 100ft below the surface, the entrances are enclosed under the floors of homes, mosques and schools - allowing fighters to move unseen between homes and alleyways within Gaza.
It is used by the warped group to transport people and goods as well as store rocks and ammunition.
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The tunnels are understood to be connected to launch pits where rockets have been fired from towards Israeli areas.
Hamas' command and control centres are also housed in the intricate system away from Israel's watch.
And it's understood the entire network is heavily laden with booby traps and homemade bombs.
Each tunnel is reinforced with concrete and some are so narrow fighters are unable to stand up in them.
Others, however, are much more spacious - allowing terrorists to run through them and transport weapons and contraband.
They are extremely difficult to detect from the air and have long frustrated Israel's military as despite being armed with top-of-the-range equipment, they have so far been unable to wipe them out.
Dr Daphné Richemond-Barak, an expert on underground warfare who teaches at Israel's Reichman University, said Hamas militants "perfected the art" of tunnel building.
She told the : "First of all, Hamas has had plenty of time to booby-trap the entire network.
"They could kidnap [the soldiers in surprise attacks]. And then you have all the other risks - running out of oxygen, fighting the enemy in one-on-one combat, and rescuing wounded soldiers becomes virtually impossible.
"Even if you don't go inside the tunnel, to secure an area where you suspect that tunnels might be present is very different from just securing an area in general.
"Here, you have to secure something that is invisible."
'UNCHARTERED TERRITORY'
A counter-terrorism expert has warned because of this, hostages snatched by Hamas gunmen could be hidden in the tunnels.
Author Samuel Katz, who spent years observing elite special units of Israel's Defence Forces, said there are multiple locations where captives could be held and described it as "uncharted territory."
After storming across the border on October 7, Hamas gunmen massacred hundreds of men, women and children in towns and at a music festival - while up to 199 people were also taken hostage.
The exact size of the network is unclear - but in 2021 Hamas claimed to have dug out 311-miles worth of tunnels.
Construction ramped up in 2007 after Hamas took control of the enclave and were initially built between Gaza and Egypt to smuggle goods in a brazen bid to avoid the Israeli blockade.
But by 2013, the network moved away from the Egyptian border and instead pivoted towards Israel.
The underground maze is now understood to sprawl for miles through the Gaza Strip - with some touching Israel packed with explosives.
As tensions hit boiling point between Israel and Gaza in 2014, the IDF said it had "neutralised" 32 tunnels along the border.
It sparked a huge reconstruction the following year as Hamas instructed heavy machinery to speed up the work, which was largely funded by Iran, the Sunday Telegraph reported.
In 2021, the IDF said it had destroyed more than 60 miles of the passages in airstrikes - but Hamas insisted just 15 miles were blasted.
Israeli forces buried Hamas leaders alive by tricking them into bolting underground then blitzing their network of tunnels.
Commanders tweeted that an attack on the Gaza Strip was under way at the same time that a bombardment from jets, tanks and gunboats erupted.
Hamas fighters scurried to grab hidden weapons to prepare for an expected surge of Israeli troops.
But the tweet was fake, and devastating bunker-buster airstrikes then rained down on 150 targets.
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Scores are believed to have died as the tunnels were smashed by 450 missiles in 40 minutes.