One of the stated missions of the Israeli airforce in the four weeks since the war broke out has been destroying Hamas infrastructure in Gaza through aerial bombardment.
A key target has been Hamas’s vast network of underground tunnels, which enable it to smuggle and stockpile weapons.
But Israeli ground forces are likely to be needed to clear out the tunnel network known as “Gaza’s Metro”, according to former US officials and military officers.
Bradley Bowman, a former US army officer and national security adviser, told US media network NBC: “A significant number of Hamas terrorists will likely be able to survive airstrikes by hiding in the tunnels.
“It is probably safe to assume that Hamas has stocked those tunnels with significant quantities of food, water, weapons, and ammunition.”
Military analyst Sean Bell said the tunnels help make the expected entry into Gaza City, which Israel claims to have encircled, a “completely different game”.
General Lord Dannatt, speaking to Sky News, said those abducted on 7 October were “undoubtedly” being held in some of the 300 miles of underground tunnels.
“In the annals of military history, this is going to be one of the most difficult operations that any army has got to carry out: How to try and achieve their objective of destroying Hamas without being complicit in the killing of over 230 hostages.
“It is a real nightmare, and frankly, it is going to be a challenge and I can’t see easily how the Israelis are going to do it other than be there for the long haul and hope eventually to smoke Hamas out.”
What are the tunnels and when were they created?
Tunnels dug in Gaza were originally used for smuggling goods in and out of Egypt to circumvent an Israeli blockade. But Palestinian militants built up the tunnels to move rockets and rocket launchers, shield militants from detection by Israeli satellites and aircraft and to stage attacks into Israeli territory.
The vast underground system includes storage rooms, electrical generators, command centres and supplies for Hamas’s fighters, according to the Israeli military.
The network has “dozens of access points located throughout Gaza”, and many of the tunnel entrances are next to civilian residences and even hospitals, the IDF says.
Mohammed Deif, the commander of the Qassam Brigades, the military wing of Hamas, is believed to be the mastermind behind the tunnel system, according to Israeli media reports.
Since 2006, Hamas militants have dug tunnels inside Israeli territory and staged a series of surprise attacks. As a result, Israel built a specially designed 40-mile underground concrete barrier to try to detect tunnel construction in Gaza. The barrier helped Israel uncover a tunnel in 2020 before Hamas could use the passage to mount an attack inside Israel, according to the IDF.
Some of the tunnels are 18 metres below ground, NBC News has previously reported.