From Israel’s perspective, everything is going according to plan in the war against the Islamist Hamas in the Gaza Strip. “We are on the verge of destroying the military system in the northern Gaza Strip. There is still a lot to do, but we are well on the way,” said Chief of General Staff Herzi Halevi during a visit to the troops in the approximately 40-kilometer-long coastal strip – and announced to target “more and more regions”. Experts expect that there could soon be fighting on the ground in the south.

In the northern city of Gaza, where hundreds of thousands of people lived before the war, Hamas already appears weakened. Israeli soldiers demonstratively hoisted Israeli flags on the beach and took photos of themselves in the parliament building. The military reports useful information for the secret services, thousands of terrorists killed and Hamas strongholds captured – including hospitals with “hidden command centers” of the terrorists. But the successes could be just the beginning of a long mission for Israeli ground forces.

The terrorist organization Hamas has largely lost control above ground in the north of the Gaza Strip, “but there is still a long way to go before the entire military capacity is eliminated,” says Harel Chorev, a Middle East expert at Tel Aviv University. A decisive factor is Hamas’s extensive tunnel system.

Thousands of fighters could have holed up in the intricate network of tunnels. It is estimated to be around 500 kilometers long. An escape of numerous terrorists from the north to the south is likely, says Chorev.

More than 300 tunnel shafts and various underground locations are said to have already been destroyed by the military. “Our particular attention is on what is underground,” military spokesman Daniel Hagari said on Thursday.

In addition to air strikes, there are many methods for destroying the tunnel structure, said Orbach. “You can flood the tunnels, for example with seawater or sewage.” The military also has special robots that are sent into shafts, some of which are up to 80 meters deep. Dogs are also in use.

The biggest problem, however, is the hostage issue. The army suspects that at least some of the approximately 240 people kidnapped by Hamas terrorists on October 7th were in the tunnels.

It is unclear how many Hamas members are hidden underground. Military historian Danny Orbach from the Hebrew University in Jerusalem estimates: several thousand. According to the Israeli military, there were around 30,000 Hamas fighters before the war began on October 7th. According to Israeli estimates, more than 4,000 have been killed since then. There is currently no information on this from Palestinian sources.

Orbach does not expect any imminent fighting in the tunnels. “The Israeli military will only consider this in individual cases where there is no other option,” says Orbach. There is a special unit specially trained for this case. “But tunnel fights carry a very high risk.” There is no GPS in the tunnel, there is only little light, shots could ricochet off the walls and hit the soldiers themselves.

In addition, the tunnels are Hamas’ territory. “They’ve probably been preparing for this scenario for years,” says Orbach. According to him, the Israeli soldiers were confronted above ground with explosive traps on doors, windows and tunnel entrances. “In the tunnels this could become even more extreme.” Last week, four special forces soldiers were killed by an explosive device in a tunnel shaft.

At the same time, the military knows that Hamas cannot “stay underground indefinitely.” Food and fuel would eventually run out. “Tunnels can no longer be lit or ventilated.” It is difficult to say whether and how much supplies could be smuggled from Egypt via the tunnels to Gaza. “Smuggling at the moment is very risky, but probably limited in small quantities,” suspects Orbach. “If they haven’t already escaped to Egypt via the tunnels.”

Orbach and other observers also believe it is likely that the fighting will shift to the south of the Gaza Strip. The Israeli military’s goal is to weaken Hamas so much that it collapses from within, says Orbach. Every single member doesn’t have to be killed for this. However, it must be avoided that the terrorist organization can gain strength again elsewhere – for example in Khan Yunis, a city in the south of the coastal strip.

This week, the Israeli military dropped leaflets in Arabic over Khan Yunis. People should move to “the known safe zone.” According to local media, panic broke out among residents of the affected neighborhoods.

According to the UN, almost 1.6 million of the approximately 2.2 million inhabitants of the approximately 40 kilometer long coastal area are fleeing as a result of the fighting. Most of them moved from the north towards the south. But air raids also occur regularly there. A possible ground offensive could worsen the humanitarian emergency there without being devastating.

Orbach has no doubt that a ground operation is also planned in the south. “Israel doesn’t want Hamas to get too comfortable in the south,” he says. In general, the war is not expected to end soon. “The intensity will change, but the fighting could last for months.” Where they relocated remains to be seen.