Many of the military lessons that Hamas has learnt from Hizbollah stem from a fateful moment in 1992 when Israel deported about 400 Palestinians, including Hamas leaders, to Lebanon and abandoned them in midwinter on a mountainside in no-man’s land.

Predominantly Shia Iran and Hizbollah saw that as an opportunity to co-opt the Sunni Hamas, after having cultivated the Palestinian Islamic Jihad in the Gaza Strip, a smaller militant group that is also in this battle. Israeli officials say Hizbollah has shared rocket technology, training and other techniques with Hamas.

Beirut has since become home to several Hamas chiefs and, in time, Hamas began to build a military presence in Lebanon — as demonstrated when a suspected Hamas weapons depot in Tyre exploded in late 2021.

Hamas has since steadily improved the quality of its armaments, smuggling in components to convert dumb rockets into guided precision weapons, and even building an underwater drone.

According to Hamas, the group now makes “Mutabar-1” shoulder-fired anti-aircraft missiles, which it says can take out Israeli helicopters, and “al-Yassin” anti-tank rockets, which it claims can penetrate the reactive armour of Israel’s Merkava tanks. Hamas fighters using the Mubar-1 air defence system Still from Hamas published footage showing the homemade ‘Mubar-1’ short-range air defence system © Eyepress via Reuters

Meanwhile, it has developed an urban style of warfare conditioned by its need to counter Israel’s technological and air superiority by forcing the battle down to gritty street fighting.

“Hamas is more Vietcong than Isis,” said Hokayem, referring to the communist fighters that ultimately beat US forces during the Vietnam war, and the jihadi group that Israel likens to Hamas.

Just as the Vietcong did in Vietnam, Hamas has turned Gaza into a fortress of barricades and mouse holes — including a 400km network of tunnels that Hamas fighters can shelter in during Israeli air strikes and use to attack Israeli forces from the rear.

As Israeli troops move deeper into Gaza, Hamas is likely to try to use above-ground ambushes, quick strikes and camouflaged bombs to wear down Israel’s largely civilian army of reservists and bog them down in street fighting.

Bilal Y Saab, an associate fellow at the Chatham House think-tank in London, said: “Hamas doesn’t have a codified doctrine. Its approach is mostly about damaging and hurting the Israelis as much as possible, using a mix of hybrid and conventional forces.”

“Operations are also highly decentralised. There is a sort of cellular military structure, where every company operates on its own,” he said. An Israeli Merkava tank close to the Israeli border with the northern Gaza Strip An Israeli Merkava tank close to the border with the northern Gaza Strip. Hamas says its ‘al-Yassin’ rockets can penetrate the tanks © Aris Messinis/AFP/Getty Images

Hamas’s propaganda operations are another important component. Downed Israeli helicopters, destroyed tanks or captured soldiers will help the militant group project an image of victory, military analysts said.

At the same time, rockets fired from hidden launchers seek to take the fight deep into Israeli territory and bolster Hamas’s support base — such as when the Ben Gurion international airport in Tel Aviv was shut down during the 50-day 2014 war.

Another lesson that Hamas copied from other militant groups is the importance of secure communications. While Hizbollah has built its own fibre optic network, Hamas has maintained operational security by going “stone age” and using hard-wired phone lines while eschewing devices that are hackable or emit an electronic signature.

One reason Israel was unable to predict the October 7 attack, said one Israeli official, was that it was listening to “the wrong lines”. Crucial military information was meanwhile shared either over that “analogue” system, or another encrypted system, maybe imported from Iran, that was unknown to Israel.

It is a technological sleight of hand that holds a powerful warning for the Israeli ground attack.

“What else were they hiding?” the Israeli official said. “You don’t think we are asking ourselves the same question?”